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Origin and Evolution of Man

Table of contents, introduction, earliest ancestor, process of human evolution, neanderthals.

Homo sapiens , the most prominent species on earth is the result of over 7 million years of evolution. The traces of human evolution have been obtained through fossil records, and morphological, physiological and embryological studies.

Man belongs to the family Hominidae of the order Primates. Humanlike apes belong to the same order. With the passage of time, their ancestors evolved and became more and more different.

The first-ever ancestors of humans are believed to have originated in Africa, eventually migrating to Europe, Asia and the rest of the world.

Ardipithecus were one of the earliest ancestors to have been discovered, with fossils dating back more than 4.4 million years old. The details of human evolution are still debated as fossil evidence of many ancestors is quite vague. In fact, instead of the human evolution tree, a more accurate analogy could be drawn to an evolutionary bush.

Charles Darwin never implied the fact that humans evolved from apes, although, many of his fellow contemporaries insisted that he had. Furthermore, the concept of a “missing link” between apes and humans was considered preposterous by scientists because we have evolved alongside the great apes. However, we do have a common ancestor that lived roughly 7 million years ago. Furthermore, evolution points to the presence of “nodal fossils”, meaning that humans evolved gradually, as opposed to a sudden change.

The evolution process involves a series of changes that cause the species to either adapt to the environment or become extinct. Evolution is the result of changes in the genetic material of humans. It does not change a single organism, but the entire group of organisms belonging to the same species.

Man originated through several stages:

Dryopethicus

It is the earliest known ancestor of man. They were found in some parts of Africa, Asia and Europe. The evolution of man began with him. Dryopethicus was followed by Australopithecus.

Australopithecus

These were 1.2 metres tall and could walk upright. They inhabited the African mainland. They had large jaws and human-like teeth.

Homo habilis

They were five feet tall and could make use of tools. They are believed to have been able to speak.

Homo erectus

They were more evolved beings. They were also upright and had a larger brain size. They had a prominent speech. They invented fire and were carnivorous.

Homo sapiens

These are modern men. They developed the power of thinking, used tools, were omnivorous and produced art. Their brain size was reduced to 1300 cc.

Homo sapiens is the only extant species of hominin around today, but a few thousand years ago, there were a few other species that existed alongside anatomically modern humans – the Neanderthals, Denisovans and the Homo floresiensis . Today, scientists consider Neanderthals to be more of a subspecies of humans rather than a completely separate species.

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Frequently Asked Questions – FAQs

Describe the origin and evolution of humans in chronological order..

Australopithecus existed 2 mya. They used stone weapons to hunt.

Then came the first human-like hominid called Homo habilis who had brain capacities of 650-800 cc.

Homo erectus existed 1.5 mya. They had a larger brain (900 ccs) and ate meat.

Neanderthals lived 1-0.4 mya. They used hides to protect their bodies.

The modern man i.e Homo sapiens came into existance 0.75-0.1 mya.

Are evolution and speciation the same?

-The formation of new and distinct species in the course of evolution.

-The gradual development of something, especially from a simple to a more complex form.

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Darwin: From the Origin of Species to the Descent of Man

This entry offers a broad historical review of the origin and development of Darwin’s theory of evolution by natural selection through the initial Darwinian phase of the “Darwinian Revolution” up to the publication of the Descent of Man in 1871. The development of evolutionary ideas before Darwin’s work has been treated in the separate entry evolutionary thought before Darwin . Several additional aspects of Darwin’s theory of evolution and his biographical development are dealt with in other entries in this encyclopedia (see the entries on Darwinism ; species ; natural selection ; creationism ). The remainder of this entry will focus on aspects of Darwin’s theory not developed in the other entries. It will also maintain a historical and textual approach. Other entries in this encyclopedia cited at the end of the article and the bibliography should be consulted for discussions beyond this point. The issues will be examined under the following headings:

1.1 Historiographical Issues

1.2 darwin’s early reflections, 2.1. the concept of natural selection.

• 2.2. The Argument of the Published Origin

3.1 The Popular Reception of Darwin’s Theory

3.2 the professional reception of darwin’s theory, 4.1 the genesis of darwin’s descent, 4.2 darwin on mental powers, 4.3 the ethical theory of the descent of man.

• 4.4 The Reception of the Descent

5. Summary and Conclusion

Other internet resources, related entries, acknowledgments, 1. the origins of darwin’s theory.

Charles Darwin’s version of transformism has been the subject of massive historical and philosophical scholarship almost unparalleled in any other area of the history of science. This includes the continued flow of monographic studies and collections of articles on particular aspects of Darwin’s theory (Prestes 2023; R. J. Richards and Ruse 2016; Ruse 2013a, 2009a,b,c; Ruse and Richards 2009; Hodge and Radick 2009; Hösle and Illies 2005; Gayon 1998; Bowler 1996; Depew and Weber 1995; Kohn 1985a). The continuous production of popular and professional biographical studies on Darwin provides ever new insights (Ruse et al. 2013a; Johnson 2012; Desmond and Moore 1991, 2009; Browne 1995, 2002; Bowlby 1990; Bowler 1990). In addition, major editing projects on Darwin’s manuscripts and the completion of the Correspondence , project through the entirety of Darwin’s life, continue to reveal details and new insights into the issues surrounding Darwin’s own thought (Keynes [ed.] 2000; Burkhardt et al. [eds] 1985–2023; Barrett et al. [eds.] 1987). The Cambridge Darwin Online website (see Other Internet Resources ) serves as an international clearinghouse for this worldwide Darwinian scholarship, functioning as a repository for electronic versions of all the original works of Darwin, including manuscripts and related secondary materials. It also supplies a continuously updated guide to current literature.

A long tradition of scholarship has interpreted Darwin’s theory to have originated from a framework defined by endemic British natural history, a British tradition of natural theology defined particularly by William Paley (1743–1805), the methodological precepts of John Herschel (1792–1871), developed in his A Preliminary Discourse on the Study of Natural Philosophy (1830 [1987]), and the geological theories of Charles Lyell (1797–1875). His conversion to the uniformitarian geology of Charles Lyell and to Lyell’s advocacy of “deep” geological time during the voyage of the HMS Beagle (December 1831–October 1836), has been seen as fundamental in his formation (Norman 2013; Herbert 2005; Hodge 1983). Complementing this predominantly anglophone historiography has been the social-constructivist analyses emphasizing the origins of Darwin’s theories in British Political Economy (Young 1985: chps. 2, 4, 5). It has also been argued that a primary generating source of Darwin’s inquiries was his involvement with the British anti-slavery movement, a concern reaching back to his revulsion against slavery developed during the Beagle years (Desmond and Moore 2009).

A body of recent historiography, on the other hand, drawing on the wealth of manuscripts and correspondence that have become available since the 1960s (online at Darwin online “Papers and Manuscripts” section, see Other Internet Resources ) has de-emphasized some of the novelty of Darwin’s views and questions have been raised regarding the validity of the standard biographical picture of the early Darwin. These materials have drawn attention to previously ignored aspects of Darwin’s biography. In particular, the importance of his Edinburgh period from 1825–27, largely discounted in importance by Darwin himself in his late Autobiography , has been seen as critical for his subsequent development (Desmond and Moore 1991; Hodge 1985). As a young medical student at the University of Edinburgh (1825–27), Darwin developed a close relationship with the comparative anatomist Robert Edmond Grant (1793–1874) through the student Plinian Society, and in many respects Grant served as Darwin’s first mentor in science in the pre- Beagle years (Desmond and Moore 1991, chp. 1). Through Grant he was exposed to the transformist theories of Jean Baptiste Lamarck and the Cuvier-Geoffroy debate centered on the Paris Muséum nationale d’histoire naturelle (see entry on evolutionary thought before Darwin , Section 4).

These differing interpretive frameworks make investigations into the origins of Darwin’s theory an active area of historical research. The following section will explore these origins.

In its historical origins, Darwin’s theory was different in kind from its main predecessors in important ways (Ruse 2013b; Sloan 2009a; see also the entry on evolutionary thought before Darwin ). Viewed against a longer historical scenario, Darwin’s theory does not deal with cosmology or the origins of the world and life through naturalistic means, and therefore was more restricted in its theoretical scope than its main predecessors influenced by the reflections of Georges Louis LeClerc de Buffon (1707–1788), Johann Herder (1744–1803, and German Naturphilosophen inspired by Friederich Schelling (1775–1854) . This restriction also distinguished Darwin’s work from the grand evolutionary cosmology put forth anonymously in 1844 by the Scottish publisher Robert Chambers (1802–1871) in his immensely popular Vestiges of the Natural History of Creation , a work which in many respects prepared Victorian society in England, and pre-Civil War America for the acceptance of a general evolutionary theory in some form (Secord 2000; MacPherson 2015). It also distinguishes Darwin’s formulations from the theories of his contemporary Herbert Spencer (1820–1903).

Darwin’s theory first took written form in reflections in a series of notebooks begun during the latter part of the Beagle voyage and continued after the return of the Beagle to England in October of 1836 (Barrett et al., 1987). His reflections on the possibility of species change are first entered in March of 1837 (“Red Notebook”) and are developed in the other notebooks (B–E) through July of 1839 (Barrett et al. 1987; Hodge 2013a, 2009). Beginning with the reflections of the third or “D” “transmutation” Notebook, composed between July and October of 1838, Darwin first worked out the rudiments of what was to become his theory of natural selection. In the parallel “M” and “N” Notebooks, dating between July of 1838 and July of 1839, and in a loose collection called “Old and Useless Notes”, dating from approximately 1838–40, he also developed many of his main ideas on human evolution that would only be made public in the Descent of Man of 1871 (below, Section 4).

To summarize a complex issue, these Notebook reflections show Darwin proceeding through a series of stages in which he first formulated a general theory of the transformation of species by historical descent from common ancestors. He then attempted to work out a causal theory of life that would explain the tendency of life to complexify and diversify (Hodge 2013a, 2009, 1985; Sloan 1986). This causal inquiry into the underlying nature of life, and with it the search for an explanation of life’s innate tendency to develop and complexify, was then replaced by a dramatic shift in focus away from these inquiries. This concern with a causal theory of life was then replaced by a new emphasis on external forces controlling population, a thesis developed from his reading of Thomas Malthus’s (1766–1834) Essay on the Principle of Population (6th ed. 1826). For Malthus, human populaton was assumed to expand geometrically, while food supply expanded arithmetically, leading to an inevitable struggle of humans for existence. The impact of Darwin’s reading of this edition of the Essay in August of 1838, was dramatic. It enabled him to theorize the existence of a constantly-acting dynamic force behind the transformation of species.

Darwin’s innovation was to universalize the Malthusian “principle of population” to apply to all of nature. In so doing, Darwin effectively introduced what may be termed an “inertial” principle into his theory, although such language is never used in his text. Newton’s first law of motion, set forth in his Mathematical Principles of Natural Philosophy (1st ed. 1687), established his physical system upon the tendency of all material bodies to persist eternally either at rest or in uniform motion in a straight line, requiring a causal force explanation for any deviations from this initial state. But Newton did not seek a deeper metaphysical explanation of this inertial state. Law One is simply an “axiom” in Newton’s Principia. Similarly, the principle of population supplied Darwin with the assumption of an initial dynamic state of affairs that was not itself explained within the theory—there is no attempt to account causally for this tendency of living beings universally to reproduce geometrically. Similarly for Darwin, the principle of population functions axiomatically, defining a set of initial conditions from which any deviance from this ideal state demands explanation.

This theoretical shift enabled Darwin to bracket his earlier efforts to develop a causal theory of life, and focus instead on the means by which the dynamic force of population was controlled. This allowed him to emphasize how controls on population worked in company with the phenomenon of slight individual variation between members of the same species, in company with changing conditions of life, to produce a gradual change of form and function over time, leading to new varieties and eventually to new species. This opened up the framework for Darwin’s most important innovation, the concept of “natural” selection.

2. Darwinian Evolution

The primary distinguishing feature of Darwin’s theory that separates it from previous explanations of species change centers on the causal explanation he offered for how this process occurred. Prior theories, such as the theory of Jean-Baptiste Lamarck (see entry on evolutionary thought before Darwin ), relied on the inherent dynamic properties of matter. The change of species was not, in these pre-Darwinian efforts, explained through an adaptive process. Darwin’s emphasis after the composition of Notebook D on the factors controlling population increase, rather than on a dynamic theory of life grounded in vital forces, accounts for many of the differences between Darwin’s theory and those of his predecessors and contemporaries.

These differences can be summarized in the concept of natural selection as the central theoretical component of Darwinian theory. However, the exact meaning of this concept, and the varying ways he stated the principle in the Origin over its six editions (1859–1872), has given rise to multiple interpretations of the meaning of this principle in the history of Darwinism, and the different understandings of his meaning deeply affected different national and cultural receptions of his theory (see below, Section 3 .1).

One way to see the complexity of Darwin’s own thinking on these issues is to follow the textual development of this concept from the close of the Notebook period (1839) to the publication of the Origin of Species in 1859. This period of approximately twenty years involved Darwin in a series of reflections that form successive strata in the final version of his theory of the evolution of species. Understanding the historical sequence of these developments also has significance for subsequent controversies over this concept and the different readings of the Origin as it went through its successive revisions. This historical development of the concept also has some bearing on assessing Darwin’s relevance for more general philosophical questions, such as those surrounding the relevance of his theory for such issues as the concept of a more general teleology of nature.

The earliest set of themes in the manuscript elaboration of natural selection theory can be characterized as those developed through a particular form of the argument from analogy. This took the form of a strong “proportional” form of the analogical argument that equated the relation of human selection to the development of domestic breeds as an argument of the basic form: human selection is to domestic variety formation as natural selection is to natural species formation (White, Hodge and Radick 2021, chps. 4–5). This makes a direct analogy between the actions of nature with those of humans in the process of selection. The specific expressions, and changes, in this analogy are important to follow closely. As this was expressed in the first coherent draft of the theory, a 39-page pencil manuscript written in 1842, this discussion analogized the concept of selection of forms by human agency in the creation of the varieties of domestic animals and plants, to the active selection in the natural world by an almost conscious agency, a “being infinitely more sagacious than man (not an omniscient creator)” who acts over “thousands and thousands of years” on “all the variations which tended towards certain ends” (Darwin 1842 in Glick and Kohn 1996, 91). This agency selects out those features most beneficial to organisms in relation to conditions of life, analogous in its action to the selection by man on domestic forms in the production of different breeds. Interwoven with these references to an almost Platonic demiurge are appeals to the selecting power of an active “Nature”:

Nature’s variation far less, but such selection far more rigid and scrutinizing […] Nature lets <<an>> animal live, till on actual proof it is found less able to do the required work to serve the desired end, man judges solely by his eye, and knows not whether nerves, muscles, arteries, are developed in proportion to the change of external form. (Ibid., 93)

These themes were continued in the 230 page draft of his theory of 1844. Again he referred to the selective action of a wise “Being with penetration sufficient to perceive differences in the outer and innermost organization quite imperceptible to man, and with forethought extending over future centuries to watch with unerring care and select for any object the offspring of an organism produced” (Darwin 1844 in ibid., 101). This selection was made with greater foresight and wisdom than human selection. As he envisions the working of this causal agency,

In accordance with the plan by which this universe seems governed by the Creator, let us consider whether there exist any secondary means in the economy of nature by which the process of selection could go on adapting, nicely and wonderfully, organisms, if in ever so small a degree plastic, to diverse ends. I believe such secondary means do exist. (Ibid., 103).

Darwin returned to these issues in 1856, following a twelve-year period in which he published his Geological Observations on the Volcanic Islands (1844), the second edition of his Journal of Researches (1845), Geological Observations on South America (1846), the four volumes on fossil and living barnacles ( Cirripedia ) (1851, 54, 55), and Geological Observations on Coral Reefs (1851). In addition, he published several smaller papers on invertebrate zoology and on geology, and reported on his experiments on the resistance of seeds to salt water, a topic that would be of importance in his explanation of the population of remote islands.

These intervening inquiries positioned Darwin to deal with the question of species permanence against an extensive empirical background. The initial major synthesis of these investigations takes place in his long manuscript, or “Big Species Book”, commenced in 1856, known in current scholarship as the “Natural Selection” manuscript. This formed the immediate background text behind the published Origin . Although incomplete, the “Natural Selection” manuscript provides insights into many critical issues in Darwin’s thinking. It was also prepared with an eye to the scholarly community. This distinguishes its content and presentation from that of the subsequent “abstract” which became the published Origin of Species . “Natural Selection” contained tables of data, references to scholarly literature, and other apparatus expected of a non-popular work, none of which appeared in the published Origin .

The “Natural Selection” manuscript also contained some new theoretical developments of relevance to the concept of natural selection that are not found in earlier manuscripts. Scholars have noted the introduction in this manuscript of the “principle of divergence”, the thesis that organisms under the action of natural selection will tend to radiate and diversify within their “conditions of life”—the contemporary name for the complex of environmental and species-interaction relationships (Kohn 1985b, 2009). Although the concept of group divergence under the action of natural selection might be seen as an implication of Darwin’s theory from his earliest formulations of the 1830s, nonetheless Darwin’s explicit definition of this as a “principle”, and its discussion in a long late insertion in the “Natural Selection” manuscript, suggests its importance for Darwin’s mature theory. The principle of divergence was now seen by Darwin to form an important link between natural variation and the conditions of existence under the action of the driving force of population increase.

Still evident in the “Natural Selection” manuscript is Darwin’s implicit appeal to some kind of teleological ordering of the process. The action of the masculine-gendered “wise being” of the earlier manuscripts, however, has now been given over entirely to the action of a selective “Nature”, now referred to in the traditional feminine gender. This Nature,

…cares not for mere external appearance; she may be said to scrutinise with a severe eye, every nerve, vessel & muscle; every habit, instinct, shade of constitution,—the whole machinery of the organisation. There will be here no caprice, no favouring: the good will be preserved & the bad rigidly destroyed.… Can we wonder then, that nature’s productions bear the stamp of a far higher perfection than man’s product by artificial selection. With nature the most gradual, steady, unerring, deep-sighted selection,—perfect adaption [sic] to the conditions of existence.… (Darwin 1856–58 [1974: 224–225])

The language of this passage, directly underlying statements about the action of “natural selection” in the first edition of the published Origin , indicates the complexity in the exegesis of Darwin’s meaning of “natural selection” when viewed in light of its historical genesis (Ospovat 1981). The parallels between art and nature, the intentionality implied in the term “selection”, the notion of “perfect” adaptation, and the substantive conception of “nature” as an agency working toward certain ends, all render Darwin’s views on teleological purpose more complex than they are typically interpreted from the standpoint of contemporary Neo-selectionist theory (Lennox 1993, 2013). As will be discussed below, the changes Darwin subsequently made in his formulations of this concept over the history of the Origin have led to different conceptions of what he meant by this principle.

The hurried preparation and publication of the Origin between the summer of 1858 and November of 1859 was prompted by the receipt on June 18 of 1858 of a letter and manuscript from Alfred Russel Wallace (1823–1913) that outlined his remarkably similar views on the possibility of continuous species change under the action of a selection upon natural variation (Wallace 1858 in Glick and Kohn 1996, 337–45). This event had important implications for the subsequent form of Darwin’s published argument. Rapidly condensing the detailed arguments of the unfinished “Natural Selection” manuscript into shorter chapters, Darwin also universalized several claims that he had only developed with reference to specific groups of organisms, or which he had applied only to more limited situations in the manuscript. This resulted in a presentation of his theory at the level of broad generalization. The absence of tables of data, detailed footnotes, and references to the secondary literature in the published version also resulted in predictable criticisms which will be discussed below in Section 3.2 .

2.2. The Central Argument of the Published Origin

The Origin of Species by Means of Natural Selection, or the Preservaton of Favoured Races in the Struggle for Life was issued in London by the publishing house of John Murray on November 24, 1859 (Darwin 1859 [1964]). The structure of the argument presented in the published Origin has been the topic of considerable literature and can only be summarized here. Although Darwin himself described his book as “one long argument”, the exact nature of this argument is not immediately transparent, and alternative interpretations have been made of his reasoning and rhetorical strategies in formulating his evolutionary theory. (Prestes 2023; White, Hodge and Radick 2021; Hodge 2013b, 1977; Hoquet 2013; Hull 2009; Waters 2009; Depew 2009; Ruse 2009; Lennox 2005; Hodge 1983b).

The scholarly reconstruction of Darwin’s methodology employed in the Origin has taken two primary forms. One approach has been to reconstruct it from the standpoint of currently accepted models of scientific explanation, sometimes presenting it as a formal deductive model (Sober 1984). Another, more historical, approach interprets his methodology in the context of accepted canons of scientific explanation found in Victorian discussions of the period (see the entry on Darwinism ; Prestes 2023; White, Hodge and Radick 2021; Hodge 2013b, 1983b, 1977; Hoquet 2013; Hull 2009; Waters 2009; Depew 2009; Lennox 2005). The degree to which Darwin did in fact draw from the available methodological discussions of his contemporaries—John Herschel, William Whewell, John Stuart Mill—is not fully clear from available documentary sources. The claim most readily documented, and defended particularly by White, Hodge and Radick (2021) and M. J. S. Hodge (1977, 1983a), has emphasized the importance of John Herschel’s A Preliminary Discourse on the Study of Natural Philosophy (1830 [1987]), which Darwin read as a young student at Cambridge prior to his departure on the HMS Beagle in December of 1831.

In Herschel’s text he would have encountered the claim that science seeks to determine “true causes”— vera causae— of phenomena through the satisfaction of explicit criteria of adequacy (Herschel, 1830 [1987], chp. 6). This concept Newton had specified in the Principia as the third of his “Rules of Reasoning in Philosophy” (see the entry on Newton’s philosophy , Section 4). Elucidation of such causes was to be the goal of scientific explanation. Vera causae , in Herschel’s formulation, were those necessary to produce the given effects; they were truly active in producing the effects; and they adequately explained these effects.

The other plausible methodological source for Darwin’s mature reasoning was the work of his older contemporary and former Cambridge mentor, the Rev. William Whewell (1794–1866), whose three-volume History of the Inductive Sciences (Whewell 1837) Darwin read with care after his return from his round-the-world voyage (Ruse 2013c, 1975). On this reading, a plausible argument has been made that the actual structure of Darwin’s text is more closely similar to a “Whewellian” model of argument. In Whewell’s accounts of his philosophy of scientific methodology (Whewell 1840, 1858), the emphasis of scientific inquiry is, as Herschel had also argued, to be placed on the discovery of “true causes”. But evidence for the determination of a vera causa was to be demonstrated by the ability of disparate phenomena to be drawn together under a single unifying “Conception of the Mind”, exemplified for Whewell by Newton’s universal law of gravitation. This “Consilience of Inductions”, as Whewell termed this process of theoretical unification under a few simple concepts, was achieved only by true scientific theories employing true causes (Whewell 1840: xxxix). It has therefore been argued that Darwin’s theory fundamentally produces this kind of consilience argument, and that his methodology is more properly aligned with that of Whewell.

A third account, related to the Whewellian reading, is that of David Depew. Building on Darwin’s claim that he was addressing “the general naturalist public,” Darwin is seen as developing what Depew has designated as “situated argumentation”, similar to the views developed by contemporary Oxford logician and rhetorical theorist Richard Whately (1787–1863) (Depew 2009). This rhetorical strategy proceeds by drawing the reader into Darwin’s world by personal narration as it presents a series of limited issues for acceptance in the first three chapters, none of which required of the reader a considerable leap of theoretical assent, and most of which, such as natural variation and Malthusian population increase, had already been recognized in some form in the literature of the period.

As Darwin presented his arguments to the public, he opens with a pair of chapters that draw upon the strong analogy developed in the manuscripts between the action of human art in the production of domestic forms, and the actions of selection “by nature.” The resultant forms are presumed to have arisen through the action of human selection on the slight variations existing between individuals within the same species. The interpretation of this process as implying directional, and even intentional, selection by a providential “Nature” that we have seen in the manuscripts was, however, downplayed in the published work through the importance given by Darwin to the role of “unconscious” selection, a concept not encountered in the Natural Selection manuscript. Such selection denotes the practice even carried out by aboriginal peoples who simply seek to maintain the integrity and survival of a breed or species by preserving the “best” forms.

The domestic breeding analogy is, however, more than a decorative rhetorical strategy. It repeatedly functions for Darwin as the principal empirical example to which he could appeal at several places in the text as a means of visualizing the working of natural selection in nature, and this appeal remains intact through the six editions of the Origin.

From this model of human selection working on small individual natural variations to produce the domestic forms, Darwin then developed in the second chapter the implications of “natural” variation, delaying discussion of the concept of natural selection until Chapter IV. The focus of the second chapter introduces another important issue. Here he extends the discussion of variation developed in Chapter I into a critical analysis of the common understanding of classification as grounded on the definition of species and higher groups based on the possession of essential defining properties. It is in this chapter that Darwin most explicitly develops his own position on the nature of organic species in relation to his theory of descent. It is also in this chapter that he sets forth the ingredients for his attack on one meaning of species “essentialism”.

Darwin’s analysis of the “species question” involves a complex argument that has many implications for how his work was read by his contemporaries and successors, and its interpretation has generated a considerable literature (see the entries on species and Darwinism ; Mallet 2013; R. A. Richards 2010; Wilkins 2009; Stamos 2007; Sloan 2009b, 2013; Beatty 1985).

Prior tradition had been heavily affected by eighteenth-century French naturalist Buffon’s novel conception of organic species in which he made a sharp distinction between “natural” species, defined primarily by fertile interbreeding, and “artificial” species and varieties defined by morphological traits and measurements upon these (see the entry on evolutionary thought before Darwin , Section 3.3). This distinction was utilized selectively by Darwin in an unusual blending of two traditions of discussion that are conflated in creative ways in Darwin’s analysis.

Particularly as the conception of species had been discussed by German natural historians of the early nineteenth-century affected by distinctions introduced by philosopher Immanuel Kant (1724–1804), “Buffonian” species were defined by the material unity of common descent and reproductive continuity. This distinguished them by their historical and material character from the taxonomic species of the “Linnean” tradition of natural history. This distinction between “natural” and “logical” species had maintained a distinction between problems presented in the practical classification of preserved specimens, distinguished by external characters, and those relating to the unity of natural species, which was grounded upon reproductive unity and the sterility criterion (Sloan 2009b).

Remarkable in Darwin’s argument is the way in which he draws selectively in his readings from these two preexistent traditions to undermine the different grounds of species “realism” assumed within both of these traditions of discourse. One framework—what can be considered in his immediate context the “Linnean” tradition—regarded species in the sense of universals of logic or class concepts, whose “reality” was often grounded on the concept of divine creation. The alternative “Buffonian” tradition viewed species more naturalistically as material lineages of descent whose continuity was determined by some kind of immanent principle, such as the possession of a conserving “internal mold” or specifying vital force (see evolutionary thought before Darwin 3.3). The result in Darwin’s hands is a complex terminological interweaving of concepts of Variety, Race, Sub-species, Tribe, and Family that can be shown to be a fusion of different traditions of discussion in the literature of the period. This creative conflation also led to many confusions among his contemporaries about how Darwin actually did conceive of species and species change in time.

Darwin addresses the species question by raising the problems caused by natural variation in the practical discrimination of taxa at the species and varietal levels, an issue with which he had become closely familiar in his taxonomic revision of the Sub-class Cirripedia (barnacles) in his eight-year study on this group. Although the difficulty of taxonomic distinctions at this level was a well-recognized problem in the literature of the time, Darwin subtly transforms this practical problem into a metaphysical ambiguity—the fuzziness of formal taxonomic distinctions created by variation in preserved specimens is seen to imply a similar ambiguity of “natural” species boundaries.

We follow this in reading how natural variation is employed by Darwin in Chapter Two of the Origin to break down the distinction between species and varieties as these concepts were commonly employed in the practical taxonomic literature. The arbitrariness apparent in making distinctions, particularly in plants and invertebrates, meant that such species were only what “naturalists having sound judgment and wide experience” defined them to be ( Origin 1859 [1964], 47). These arguments form the basis for claims by his contemporaries that Darwin was a species “nominalist”, who defined species only as conventional and convenient divisions of a continuum of individuals.

But this feature of Darwin’s discussion of species captures only in part the complexity of his argument. Drawing also on the tradition of species realism developed within the “Buffonian” tradition, Darwin also affirmed that species and varieties are defined by common descent and material relations of interbreeding. Darwin then employed the ambiguity of the distinction between species and varieties created by individual variation in practical taxonomy to undermine the ontological fixity of “natural” species. Varieties are not simply the formal taxonomic subdivisions of a natural species as conceived in the Linnaean tradition. They are, as he terms them, “incipient” species (ibid., 52). This subtly transformed the issue of local variation and adaptation to circumstances into a primary ingredient for historical evolutionary change. The full implications to be drawn from this argument were, however, only to be revealed in Chapter Four of the text.

Before assembling the ingredients of these first two chapters, Darwin then introduced in Chapter Three the concept of a “struggle for existence”. This concept is introduced in a “large and metaphorical sense” that included different levels of organic interactions, from direct struggle for food and space to the struggle for life of a plant in a desert. Although described as an application of Thomas Malthus’s parameter of geometrical increase of population in relation to the arithmetical increase of food supply, Darwin’s use of this concept in fact reinterprets Malthus’s principle, which was formulated only with reference to human population in relation to food supply. It now becomes a general principle governing all of organic life. Thus all organisms, including those comprising food for others, would be governed by the tendency to geometrical increase.

Through this universalization, the controls on population become only in the extreme case grounded directly on the traditional Malthusian limitations of food and space. Normal controls are instead exerted through a complex network of relationships of species acting one on another in predator-prey, parasite-host, and food-web relations. This profound revision of Malthus’s arguments rendered Darwin’s theory deeply “ecological” as this term would later be employed. We can cite two thought experiments employed by Darwin himself as illustrations (ibid., 72–74). The first concerns the explanation of the abundance of red clover in England. This Darwin sees as dependent on the numbers of pollinating humble bees, which are controlled in turn by the number of mice, and these are controlled by the number of cats, making cats the remote determinants of clover abundance. The second instance concerns the explanation of the abundance of Scotch Fir. In this example, the number of fir trees is limited indirectly by the number of cattle.

With the ingredients of the first three chapters in place, Darwin was positioned to assemble these together in his grand synthesis of Chapter Four on “natural” selection. In this long discussion, Darwin develops the main exposition of his central theoretical concept. For his contemporaries and for the subsequent tradition, however, the meaning of Darwin’s concept of “natural” selection was not unambiguously evident for reasons we have outlined above, and these unclarities were to be the source of several persistent lines of disagreement and controversy.

The complexities in Darwin’s presentation of his central principle over the six editions of the published Origin served historically to generate several different readings of his text. In the initial introduction of the principle of natural selection in the first edition of Darwin’s text, it is characterized as “preservation of favourable variations and the rejection of injurious variations” (ibid., 81). When Darwin elaborated on this concept in Chapter Four of the first edition, he continued to describe natural selection in language suggesting that it involved intentional selection, continuing the strong art-nature analogy found in the manuscripts. For example:

As man can produce and certainly has produced a great result by his methodical and unconscious means of selection, what may not nature effect? Man can act only on external and visible characters: nature cares nothing for appearances, except in so far as they may be useful to any being. She can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his own good; Nature only for that of the being which she tends. Every selected character is fully exercised by her; and the being is placed under well-suited conditions of life. (Ibid., 83)

The manuscript history behind such passages prevents the simple discounting of these statements as mere rhetorical imagery. As we have seen, the parallel between intentional human selectivity and that of “nature” formed the proportional analogical model upon which the concept of natural selection was originally constructed.

Criticisms that quickly developed over the overt intentionality embedded in such passages, however, led Darwin to revise the argument in editions beginning with the third edition of 1861. From this point onward he explicitly downplayed the intentional and teleological language of the first two editions, denying that his appeals to the selective role of “nature” were anything more than a literary figure. Darwin then moved decisively in the direction of defining natural selection as the description of the action of natural laws working upon organisms rather than as an efficient or final cause of life. He also regrets in his Correspondence his mistake in not utilizing the designation “natural preservation” rather than “natural selection” to characterize his principle (letter to Lyell 28 September 1860, Burkhardt Correspondence 8, 397; also see Darwin Correspondence Project in Other Internet Resources ). In response to criticisms of Alfred Russel Wallace, Darwin then adopted in the fifth edition of 1869 his contemporary (1820–1903) Herbert Spencer’s designator, “survival of the fittest”, as a synonym for “natural selection” (Spencer 1864, 444–45; Darwin 1869, 72). This redefinition further shifted the meaning of natural selection away from the concept that can be extracted from the early texts and drafts. These final statements of the late 1860s and early 70s underlie the tradition of later “mechanistic” and non-teleological understandings of natural selection, a reading developed by his disciples who, in the words of David Depew, “had little use for either his natural theodicy or his image of a benignly scrutinizing selection” (Depew 2009, 253). The degree to which this change preserved the original strong analogy between art and nature can, however, be questioned. Critics of the use of this analogy had argued since the original formulations that the comparison of the two modes of selection actually worked against Darwin’s theory (Wallace 1858 in Glick and Kohn 1997, 343). This critique would also be leveled against Darwin in the critical review of 1867 by Henry Fleeming Jenkin discussed below.

The conceptual synthesis of Chapter Four also introduced discussions of such matters as the conditions under which natural selection most optimally worked, the role of isolation, the causes of the extinction of species, and the principle of divergence. Many of these points were made through the imaginative use of “thought experiments” in which Darwin constructed possible scenarios through which natural selection could bring about substantial change.

One prominent way Darwin captured for the reader the complexity of this process is reflected in the single diagram to appear in all the editions of the Origin . In this illustration, originally located as an Appendix to the first edition, but thereafter moved into Chapter Four, Darwin summarized his conception of how species were formed and diverged from common ancestral points. This image also served to depict the frequent extinction of most lineages, an issue developed in detail in Chapter Ten. It displayed pictorially the principle of divergence, illustrating the general tendency of populations to diverge and fragment under the pressure of population increase. It supplied a way of envisioning relations of taxonomic affinity to time, and illstrated the persistence of some forms unchanged over long geological periods in which stable conditions prevail.

Figure: Tree of life diagram from Origin of Species ( Origin 1859:“Appendix”.

Remarkable about Darwin’s diagram of the tree of life is the relativity of its coordinates. It is first presented as applying only to the divergences taking place in taxa at the species level, with varieties represented by the small lower-case letters within species A–L of a “wide ranging genus”, with the horizontal lines representing time segments measured in terms of a limited number of generations. However, the attentive reader could quickly see that Darwin’s destructive analysis of the distinction between “natural” and “artificial” species in Chapter Two, implied the relativity of the species-variety distinction, this diagram could represent eventually all organic relationships, from those at the non-controversial level of diverging varieties within fixed species, to those of the relations of Species within different genera. Letters A–L could also represent taxa at the level of genera, families or orders. The diagram can thus be applied to relationships between all levels of the Linnaean hierarchy with the time segments representing potentially vast expanses of time, and the horizontal spread of branches the degree of taxonomic divergence over time. In a very few pages of argument, the diagram was generalized to represent the most extensive group relations, encompassing the whole of geological time. Extension of the dotted lines at the bottom could even suggest, as Darwin argues in the last paragraph of the Origin , that all life was a result of “several powers, having been originally breathed into a few forms or into one” (Darwin 1859 [1964], 490). This could suggest a single naturalistic origin of all original forms either by material emergence, or through the action of a vitalistic power of life. Darwin’s use of Biblical language could also be read as allowing for the action of a supernatural cause.

In response to criticisms concerning this latter point, Darwin quickly added to the final paragraph in the second edition of 1860 the phrase “by the Creator” (1860: 484), which remained in all subsequent editions. as did the quotations on the frontispiece from familiar discussions in British natural theology concerning creation by secondary causation. Conceptual space was thereby created for the reading of the Origin by some contemporaries, notably by the Harvard botanist Asa Gray (1810–88), as compatible with traditional natural theology (Gray 1860).

The sweep of the theoretical generalization that closed the natural selection chapter, one restated even more generally in the final paragraph of the book, required Darwin to deal with several obvious objections to the theory that constitute the main “defensive” chapters of the Origin (Five–Nine), and occupy him through the numerous revisions of the text between 1859 and 1872. As suggested by David Depew, the rhetorical structure of the original text developed in an almost “objections and response” structure that resulted in a constant stream of revisions to various editions of the original text as Darwin engaged his opponents (Depew 2009; Peckham 2006). Anticipating at first publication several obvious lines of objection, Darwin devoted much of the text of the original Origin to offering a solution in advance to predictable difficulties. As Darwin outlined these main lines of objection, he discussed, first, the apparent absence of numerous slight gradations between species, both in the present and in the fossil record, of the kind that would seem to be predictable from the gradualist workings of the theory (Chps. Six, Nine). Second, the gradual development of organs and structures of extreme complexity, such as the vertebrate eye, an organ which had since Antiquity served as a mainstay of the argument for external teleological design (Chp. Six). Third, the evolution of the elaborate instincts of animals and the puzzling problem of the evolution of social insects that developed sterile neuter castes, proved to be a particularly difficult issue for Darwin in the manuscript phase of his work and needed some account (Chp. Seven). As a fourth major issue needing attention, the traditional distinction between natural species defined by interfertility, and artificial species defined by morphological differences, required an additional chapter of analysis in which he sought to undermine the absolute character of the interbreeding criterion as a sign of fixed natural species (Chp. Eight).

In Chapter Ten, Darwin developed his interpretation of the fossil record. At issue was the claim by Lamarckian and other transformists, as well as Cuvierian catastrophists such as William Buckland (1784–1856) (see the entry on evolutionary thought before Darwin , Section 4.1), that the fossil record displayed a historical sequence beginning with simpler plants and animals, arriving either by transformism or replacement, at the appearance of more complex forms in geological history. Opposition to this thesis of “geological progressionism” had been made by none other than Darwin’s great mentor in geology, Charles Lyell in his Principles of Geology (Lyell 1832 [1990], vol. 2, chp. xi; Desmond 1984; Bowler 1976). Darwin defended the progressionist view against Lyell’s arguments in this chapter.

To each of the lines of objection to his theory, Darwin offered his contemporaries plausible replies. Additional arguments were worked out through the insertion of numerous textual insertions over the five revisions of the Origin between 1860 and 1872, including the addition of a new chapter to the sixth edition dealing with “miscellaneous” objections, responding primarily to the criticisms of St. George Jackson Mivart (1827–1900) developed in his Genesis of Species (Mivart 1871).

For reasons related both to the condensed and summary form of public presentation, and also as a reflection of the bold conceptual sweep of the theory, the primary argument of the Origin could not gain its force from the data presented by the book itself. Instead, it presented an argument from unifying simplicity, gaining its force and achieving assent from the ability of Darwin’s theory to draw together in its final synthesizing chapters (Ten–Thirteen) a wide variety of issues in taxonomy, comparative anatomy, paleontology, biogeography, and embryology under the simple principles worked out in the first four chapters. This “consilience” argument might be seen as the best reflection of the impact of William Whewell’s methodology (see above).

As Darwin envisioned the issue, with the acceptance of his theory, “a grand untrodden field of inquiry will be opened” in natural history. The long-standing issues of species origins, if not the explanation of the ultimate origins of life, as well as the causes of their extinction, had been brought within the domain of naturalistic explanation. It is in this context that he makes the sole reference in the text to the claim that “light will be thrown on the origin of man and his history”. And in a statement that will foreshadow the important issues of the Descent of Man of 1871, he speaks of how “Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation” (ibid., 488)

3. The Reception of the Origin

The broad sweep of Darwin’s claims, the brevity of the empirical evidence actually supplied in the Origin , and the implications of his theory for several more general philosophical and theological issues, opened up a controversy over Darwinian evolution that has waxed and waned over more than 160 years. The theory was inserted into a complex set of different national and cultural receptions the study of which currently forms a scholarly industry in its own right. European, Latin American and Anglophone receptions have been most deeply studied (Bowler 2013a; Gayon 2013; Largent 2013; Glick 1988, 2013; Glick and Shaffer 2014; Engels and Glick 2008; Gliboff 2008; Numbers 1998; Pancaldi, 1991; Todes 1989; Kelly 1981; Hull 1973; Mullen 1964). To these have been added analyses of non-Western recptions (Jin 2020, 2019 a,b; Yang 2013; Shen 2016; Elshakry 2013; Pusey 1983). These analyses display common patterns in both Western and non-Western readings of Darwin’s theory, in which these receptions were conditioned, if not determined, by the pre-existing intellectual, scientific, religious, social, and political contexts into which his works were inserted.

In the anglophone world, Darwin’s theory fell into a complex social environment that in the United States meant into the pre-Civil War slavery debates (Largent 2013; Numbers 1998). In the United Kingdom it was issued against the massive industrial expansion of mid-Victorian society, and the development of professionalized science. To restrict focus to aspects of the British reading public context, the pre-existing popularity of the anonymous Vestiges of the Natural History of Creation of 1844, which had reached 11 editions and sold 23,350 copies by December of 1860 (Secord “Introduction” to Chambers 1844 [1994], xxvii]), with more editions to appear by the end of the century, certainly prepared the groundwork for the general notion of the evolutionary origins of species by the working of secondary natural laws. The Vestiges ’s grand schema of a teleological development of life, from the earliest beginnings of the solar system in a gaseous nebula to the emergence of humanity under the action of a great “law of development”, had also been popularized for Victorian readers by Alfred Lord Tennyson’s epic poem In Memoriam (1850). This Vestiges backdrop provided a context in which some could read Darwin as supplying additional support for the belief in an optimistic historical development of life under teleological guidance of secondary laws with the promise of ultimate historical redemption. Such readings also rendered the Origin seemingly compatible with the progressive evolutionism of Darwin’s contemporary Herbert Spencer (see the entry on Herbert Spencer ). Because of these similarities, Spencer’s writings served as an important vehicle by which Darwin’s views, modified to fit the progressivist views expounded by Spencer, were first introduced in non-Western contexts (Jin 2020, 2019 a,b; Lightman [ed.] 2015; Pusey 1983). Such popular receptions ignored or revised Darwin’s concept of evolution by natural selection to fit these progressivist alternatives.

Outside the United Kingdom, the receptions of Darwin’s work display the importance of local context and pre-existent intellectual and social conditions. Three examples—France, Germany, and China—can be elaborated upon. In France, Darwin’s theory was received against the background of the prior debates over transformism of the 1830s that pitted the theories of Lamarck and Etienne Geoffroy St. Hilaire against Cuvier (Gayon 2013; entry on evolutionary thought before Darwin , 4.1). At least within official French Academic science, these debates had been resolved generally in favor of Cuvier’s anti-transformism. The intellectual framework provided by the “positive philosophy” of Auguste Comte (1798–1857) also worked both for and against Darwin. On one hand, Comte’s emphasis on the historical progress of science over superstition and metaphysics allowed Darwin to be summoned in support of a theory of the progress of science. The Origin was so interpreted in the preface to the first French translation of the Origin made by Clémence Royer (Harvey 2008). On the other hand, the Comtean three stages view of history, with its claim of the historical transcendence of speculative and metaphysical periods of science by a final period of experimental science governed by determinate laws, placed Darwinism in a metaphysical phase of speculative nature philosophy. This view is captured by the assessment of the leading physiologist and methodologist of French Science, Claude Bernard (1813–78). As he stated this in his 1865 treatise on scientific methodology, Darwin’s theory was to be regarded with those of “a Goethe, an Oken, a Carus, a Geoffroy Saint Hilaire”, locating it within speculative philosophy of nature rather than granting it the status of “positive” science (Bernard 1865 [1957], 91–92]).

In the Germanies, Darwin’s work entered a complex social, intellectual and political situation in the wake of the failed efforts to establish a liberal democracy in 1848. It also entered an intellectual culture strongly influenced by the pre-existent philosophical traditions of Kant, Schelling’s Naturphilosophie , German Romanticism, and the Idealism of Fichte and Hegel (R. J. Richards 2002, 2008, 2013; Gliboff 2007, 2008; Mullen 1964). These factors formed a complex political and philosophical environment into which Darwin’s developmental view of nature and theory of the transformation of species was quickly assimilated, if also altered. Many readings of Darwin consequently interpreted his arguments against the background of Schelling’s philosophy of nature. The marshalling of Darwin’s authority in debates over scientific materialism were also brought to the fore by the enthusiastic advocacy of Darwinism in Germany by University of Jena professor of zoology Ernst Heinrich Haeckel (1834–1919). More than any other individual, Haeckel made Darwinismus a major player in the polarized political and religious disputes of Bismarckian Germany (R. J. Richards 2008). Through his polemical writings, such as the Natural History of Creation (1868), Anthropogeny (1874), and Riddle of the Universe (1895–99), Haeckel advocated a materialist monism in the name of Darwin, and used this as a stick with which to beat traditional religion. Much of the historical conflict between religious communities and evolutionary biology can be traced back to Haeckel’s polemical writings, which went through numerous editions and translations, including several English and American editions that appeared into the early decades of the twentieth century.

To turn to a very different context, that of China, Darwin’s works entered Chinese discussions by a curious route. The initial discussions of Darwinian theory were generated by the translation of Thomas Henry Huxley’s 1893 Romanes Lecture “Evolution and Ethics” by the naval science scholar Yan Fu (1854–1921), who had encountered Darwinism while being educated at the Royal Naval College in Greenwich from 1877 to 1879. This translation of Huxley’s lecture, published in 1898 under the name of Tianyan Lun , was accompanied with an extensive commentary by Yan Fu that drew heavily upon the writings of Herbert Spencer which Yan Fu placed in opposition to the arguments of Huxley. This work has been shown to have been the main vehicle by which the Chinese learned indirectly of Darwin’s theory (Jin 2020, 2019 a, b; Yang 2013; Pusey 1983). In the interpretation of Yan Fu and his allies, such as Kan Yuwei (1858–1927), Darwinism was given a progressivist interpretation in line with aspects of Confucianism.

Beginning in 1902, a second phase of Darwinian reception began with a partial translation of the first five chapters of the sixth edition of the Origin by the Chinese scientist, trained in chemistry and metallurgy in Japan and Germany, Ma Junwu (1881–1940). This partial translation, published between 1902 and 1906, again modified the text itself to agree with the progressive evolutionism of Spencer and with the progressivism already encountered in Yan Fu’s popular Tianyan Lun. Only in September of 1920 did the Chinese have Ma Junwu’s full translation of Darwin’s sixth edition. This late translation presented a more faithful rendering of Darwin’s text, including an accurate translation of Darwin’s final views on natural selection (Jin 2019 a, b). As a political reformer and close associate of democratic reformer Sun Yat-Sen (1866–1925), Ma Junwu’s interest in translating Darwin was also was involved with his interest in revolutionary Chinese politics (Jin 2019a, 2022).

The reception of the Origin by those who held positions of professional research and teaching positions in universities, leadership positions in scientific societies, and employment in museums, was complex. These individuals were typically familiar with the empirical evidence and the technical scientific issues under debate in the 1860s in geology, comparative anatomy, embryology, biogeography, and classification theory. This group can usually be distinguished from lay interpreters who may not have made distinctions between the views of Lamarck, Chambers, Schelling, Spencer, and Darwin on the historical development of life.

If we concentrate attention on the reception by these professionals, Darwin’s work received varied endorsement (Hull 1973). Many prominent members of Darwin’s immediate intellectual circle—Adam Sedgwick, William Whewell, Charles Lyell, Richard Owen, and Thomas Huxley—had previously been highly critical of Chambers’s Vestiges in the 1840s for its speculative character and its scientific incompetence (Secord 2000). Darwin himself feared a similar reception, and he recognized the substantial challenge facing him in convincing this group and the larger community of scientific specialists with which he interacted and corresponded widely. With this group he was only partially successful.

Historical studies have revealed that only rarely did members of the scientific elites accept and develop Darwin’s theories exactly as they were presented in his texts. Statistical studies on the reception by the scientific community in England in the first decade after the publication of the Origin have shown a complicated picture in which there was neither wide-spread conversion of the scientific community to Darwin’s views, nor a clear generational stratification between younger converts and older resisters, counter to Darwin’s own predictions in the final chapter of the Origin (Hull et al. 1978). These studies also reveal a distinct willingness within the scientific community to separate acceptance of Darwin’s more general claim of species descent with modification from common ancestors from the endorsement of his explanation of this descent through the action of natural selection on slight morphological variations.

Of central importance in analyzing this complex professional reception was the role assigned by Darwin to the importance of normal individual variation as the source of evolutionary novelty. As we have seen, Darwin had relied on the novel claim that small individual variations—the kind of differences considered by an earlier tradition as merely “accidental”—formed the raw material upon which, by cumulative directional change under the action of natural selection, major changes could be produced sufficient to explain the origin and subsequent differences in all the various forms of life over time. Darwin, however, left the specific causes of this variation unspecified beyond some effect of the environment on the sexual organs. Variation was presented in the Origin with the statement that “the laws governing inheritance are quite unknown” (Darwin 1859 [1964], 13). In keeping with his commitment to the gradualism of Lyellian geology, Darwin also rejected the role of major “sports” or other sources of discontinuous change in this process.

As critics focused their attacks on the claim that such micro-differences between individuals could be accumulated over time without natural limits, Darwin began a series of modifications and revisions of the theory through a back and forth dialogue with his critics that can be followed in his revisions to the text of the Origin . In the fourth edition of 1866, for example, Darwin inserted the claim that the continuous gradualism depicted by his branching diagram was misleading, and that transformative change does not necessarily go on continuously. “It is far more probable that each form remains for long periods unaltered, and then again undergoes modification” (Darwin 1866, 132; Peckham 2006, 213). This change-stasis-change model allowed variation to stabilize for a period of time around a mean value from which additional change could then resume. Such a model would, however, presumably require even more time for its working than the multi-millions of years assumed in the original presentation of the theory.

The difficulties in Darwin’s arguments that had emerged by 1866 were highlighted in a lengthy and telling critique in 1867 by the Scottish engineer Henry Fleeming Jenkin (1833–1885) (typically Fleeming Jenkin). Using an argument previously raised in the 1830s by Charles Lyell against Lamarck, Fleeming Jenkin cited empirical evidence from domestic breeding that suggested a distinct limitation on the degree to which normal variation could be added upon by selection (Fleeming Jenkin 1867 in Hull 1973). Using a loosely mathematical argument, Fleeming Jenkin argued that the effects of intercrossing would continuously swamp deviations from the mean values of characters and result in a tendency of the variation in a population to return to mean values over time. It is also argued that domestic evidence does not warrant an argument for species change. For Fleeming Jenkin, Darwin’s reliance on continuous additive deviation was presumed to be undermined by these arguments, and only more dramatic and discontinuous change—something Darwin explicitly rejected—could account for the origin of new species.

Fleeming Jenkin also argued that the time needed by Darwin’s theory to account for the history of life under the gradual working of natural selection was simply unavailable from scientific evidence, supporting this claim by an appeal to the physical calculations of the probable age of the solar system presented in publications by his mentor, the Glasgow physicist William Thompson (Lord Kelvin, 1824–1907) (Burchfield 1975). On the basis of Thompson’s quantitative physical arguments concerning the age of the sun and solar system, Fleeming Jenkin judged the time since the presumed first beginnings of life to be insufficient for the Darwinian gradualist theory of species transformation to have taken place.

Jenkin’s multi-pronged argument gave Darwin considerable difficulties and set the stage for more detailed empirical inquiries into variation and its causes by Darwin’s successors. The time difficulties were only resolved in the twentieth-century with the discovery of radioactivity that could explain why the sun did not lose heat in accord with Newtonian principles.

As a solution to the variation question, Darwin developed his “provisional hypothesis” of pangenesis, which he presented the year after the appearance of the Fleeming Jenkin review in his two-volume Variation of Plants and Animals Under Domestication (Darwin 1868; Olby 2013). Although this theory had been formulated independently of the Jenkin review (Olby 1963), in effect it functioned as Darwin’s reply to Jenkin’s critique. The pangenesis theory offered a causal theory of variation and inheritance through a return to a theory resembling Buffon’s theory of the organic molecules proposed in the previous century (see entry on evolutionary thought before Darwin section 3.2). Invisible material “gemmules” were presumed to exist within the cells. According to theory, these were subject to external alteration by the environment and other external causes. The gemmules were then shed continually into the blood stream (the “transport” hypothesis) and assembled by “mutual affinity for each other, leading to their aggregation either into buds or into the sexual elements” (Darwin 1868, vol. 2, 375). In this form they were then transmitted—the details were not explained—by sexual generation to the next generation to form the new organism out of “the modified physiological units of which the organism is built” (ibid., 377). In Darwin’s view, this hypothesis united together numerous issues into a coherent and causal theory of inheritance and explained the basis of variation. It also explained how use-disuse inheritance, a theory which Darwin never abandoned, could work.

The pangenesis theory, although not specifically referred to, seems to be behind an important distinction Darwin inserted into the fifth edition of the Origin of 1869 in his direct reply to the criticisms of Jenkin. In this textual revision, Darwin distinguished “certain variations, which no one would rank as mere individual differences”, from ordinary variations (Darwin1869, 105; Peckham 2006, 178–179). This revision shifted Darwin’s emphasis away from his early reliance on normal slight individual variation, and gave new status to what he now termed “strongly marked” variations. The latter were now the forms of variation to be given primary evolutionary significance. Presumably this strong variation was more likely to be transmitted to the offspring, although details are left unclear, and in this form major variation could presumably be maintained in a population against the tendency to swamping by intercrossing as Fleeming Jenkin had argued.

Darwin’s struggles over this issue defined a set of problems that British life scientists in particular were to deal with into the 1930s. These debates over the role of somatic variation in the evolutionary process placed Darwinism in a defensive posture that forced its supporters into major revisions in the Darwinian research program (Gayon 1998; Vorzimmer 1970). The consequence was a complex period of Darwinian history in which natural selection theory was rejected by many research, or defended in modified form by others (Bowler 1983, 2013a; Largent 2009).

4. Human Evolution and the Descent of Man

Darwin had retained his own conclusions on human evolution quietly in the background through the 1860’s while the defense of his general theory was conducted by advocates as diverse as Thomas Henry Huxley (1825–95) in England, Asa Gray (1810–88) in the United States, and Ernst Haeckel (1834–1919) in the emerging new Germany. Darwin’s own position on the “human question” remained unclear to the reading public, and his rhetorical situating of the Origin within a tradition of divine creation by secondary law, captured in the frontispiece quotations from William Whewell and Francis Bacon, allowed many before 1871 to see Darwin as more open to religious interpretations of human origins than those of some of his popularizers.

Darwin’s interest in developing his insights into the origins of human beings and the explanation of human properties through descent with modification was, however, evident in his correspondence as early as January of 1860 when he began collecting evidence on the expressions of the emotions in human beings (Browne 2002, chp. 9). He then developed a questionnaire specifically intended to gain such information from contacts in Patagonia and Tierra del Fuego (Radick 2018). Further engagement with these issues was then generated by the discussions of Lyell (1863) and A. R. Wallace (1864), both of whom suggested that natural selection could not account for the development of the “higher” rational faculties, language, and ethical motivation (R. J. Richards 1987, chp. 4). It was then in February of 1867 that Darwin decided to remove material from his massive manuscript of the Variation of Plants and Animals Under Domestication to create a “very small volume, ‘an essay on the origin of mankind’” (Darwin to Hooker, 8 February 1867 and CD to Turner, 11 February 1867, Burkhardt, Correspondence 15: 74, 80). At this time he also sent to several international correspondents a more detailed questionnaire asking for information on human emotional expression. Further impetus to develop his views was created by the arguments of William R. Greg (1809–1881) in an essay in Fraser’s Magazine (1868), with further support by arguments of A. R. Wallace in 1869, both of whom drew a sharp distinction between human properties and those of animals (R. J. Richards 1987, 172–184). These arguments denied that natural selection could explain the origins of these “higher powers”.

Darwin’s drafting of his views on human issues, begun in early 1868, expanded into a major enterprise in which he became deeply engaged with the issue of the implications of his theory for ethics. The result of this effort devoted to anthropological topics was two separate works: the Descent of Man and Selection in Relation to Sex , delivered to the publisher in June of 1870 with publication in 1871, and its companion, Expression of the Emotions in Man and Animals , which he commenced in early 1871 with publication in early 1872.

As commentators have noted, these two works differ markedly in their arguments, and reflect different relationships to Darwin’s causal theories of natural and sexual selection, with sexual selection predominting over natural selection for the major portion of the Descent , and both of these causal theories generally missing from the descriptive approach of the Expression (Radick 2018).

Sexual selection—the choosing of females by males or vice versa for breeding purposes—had received a general statement by Darwin in Chapter IV of the Origin , but this played only a minor role in the original argument, and its importance was denied by co-evolutionist A. R. Wallace. In the Descent this was now developed in extensive detail as a major factor in evolution that could even work against ordinary natural selection. Sexual selection could be marshaled to explain sexual dimorphism, and also the presence of unusual characters and properties of organisms—elaborate feeding organs, bright colors, and other seemingly maladaptive structures such as the antlers on the Irish Elk or the great horn on the Rhinoceros beetle—that would appear anomalous outcomes of ordinary natural selection working for the optimal survival of organisms in nature. In a dramatic extension of the principle to human beings, the combination of natural and sexual selection is used to explain the origins of human beings from simian ancestors. It also accounts for the sexual dimorphism in humans, and is a major factor accounting for the origin of human races (E. Richards 2017; R. A. Richards 2013).

Although the secondary causal role of sexual selection in the development of species generally was to be the main topic of the bulk of the Descent , this plays an ambiguous role initially in the “treatise on man” that occupies the initial chapters, and functions differently in his treatment of the origins of mental powers, the moral sense, and the origin of races in this opening discussion.

In constructing this presentation, Darwin reaches back to the early Notebooks that he had separated out from the “transformist” discussions to deal with his inquiries into ethics, psychology, and emotions (see Section 1.2 above). Of particular importance for the opening discussions of the Descent was the “M” notebook, commenced in July of 1838, and “N”, begun in October of that year. On occasion he also samples the collection of entries now entitled “Old and Useless Notes”, generally written between 1838 and 1840.

The initial topic of focus in the Descent deals with the far-reaching issues concerning the status and origin of human mental properties, faculties presumed traditionally to be possessed uniquely by human beings. These properties Darwin now places on an evolutionary continuum with those features of animal behavior long regarded as instinctual. In this he placed himself in opposition to the long tradition of discourse that had distinguished humans from animals due to the possession of a “rational principle” related to their possession of a rational soul. This tradition had been given a more radical foundation in the revolutionary reflections on the relation of mind and body initiated by René Descartes (1596–1650) in the middle of the seventeenth century. Descartes deepened this distinction with the separation of the two substances—thinking substance, or res cogitans , possessed only by humans, and extended material substance, res extensa that constituted the rest of the natural world, including animals and plants, rendering animals only lifeless machines without rational faculties.

Darwin’s collapse of this Cartesian barrier with his theory of human origins outlined in the Descent continued a discussion that had been a concern of his transformist predecessors, especially Jean Baptiste Lamarck (Sloan 1999). But Darwin took this issue to a new level as he interpreted the human-animal relationship in the context of his novel theory of divergent evolution from common ancestors. Darwin also broke with the view of humans as the summit of a natural teleological process. Darwin instead denies such teleological ordering, and effectively reduces human properties to those of animals—mental as well as physical—by tracing them to their origin in properties of lower organisms.

The warrant for the identification of human and animal mental properties, however, is not supported by substantial argumentation in the Descent. The opening discussions of the treatise summarize the anatomical evidence for “homologies” —true identities—between humans and animals due to descent from common ancestors, claims already set out in Chapter Thirteen of the Origin. But the transferal of this identity of structure to inner non-anatomical “mental” properties rested on premises that are not made explicit in this text, and were not identities drawn by Huxley, Wallace and Lyell, for example, in their treatments of humans in relation to evolutionary theory, although they acknowledged the anatomical continuities.

To understand Darwin’s arguments, it is useful to return to his Notebook discussions on which he was drawing for his reasoning (see above, Section 1.2). In his “C” Notebook, opened in February of 1838, Darwin has a remarkable entry that displays very early on his commitment to a metaphysical “monism”—the thesis that there is only one substance underlying both mind and body. With this goes the thesis of a parallelism of the complexity of mental properties with those of material structure. In this entry in “C” following on Darwin’s reflections on the issue of instinct, and also recording some of his observations on animals at the Regents Park zoological gardens, Darwin comments:

There is one living spirit, prevalent over this wor[l]d, (subject to certain contingencies of organic matter & chiefly heat), which assumes a multitude of forms <<each having acting principle>> according to subordinate laws.—There is one thinking […] principle (intimately allied to one kind of organic matter—brain. & which <prin> thinking principle. seems to be given or assumed according to a more extended relations [ sic ] of the individuals, whereby choice with memory, or reason ? is necessary.—) which is modified into endless forms, bearing a close relation in degree & kind to the endless forms of the living beings.— We see thus Unity in thinking and acting principle in the various shades of <dif> separation between those individuals thus endowed, & the community of mind, even in the tendency to delicate emotions between races, & recurrent habits in animals.— (Barrett 1987, 305)

As we follow these issues into the “M” Notebook, the assumption of a single “thinking principle,” allied to one kind of organic matter, seems then to underlie Darwin’s subsequent reflections on mind and matter. The “M” Notebook cites numerous “mental”properties common to humans and animals that generally parallel levels of material organization, similar to the identities expressed in the later Descent. The range of this universal extension of mental properties is far-reaching in these early discussions: consciousness and “free will” extends to all animals, including invertebrates:

With respect to free will, seeing a puppy playing cannot doubt that they have free will, if so all animals., then an oyster has & a polype (& a plant in some senses […]; now free will of oyster, one can fancy to be direct effect of organization, by the capacities its senses give it of pain or pleasure, if so free will is to mind, what chance is to matter […] (Barrett 1987, 536).

When these themes reappear in Chapter Two of the first edition of the Descent , Darwin seems to draw implicitly upon this matter-mind identity theory as an obvious consequence of his theory of descent from common ancestry. There he enumerates a long list of traditional human mental and emotional properties to claim that each of them are identities with the properties of simpler forms of life. The list is expansive: courage, deceit, play, kindness, maternal affection, self-complacency, pride, shame, sense of honor, wonder, dread, imitation, imagination, and dreaming. All are considered to be represented in a wide range of animals, with “play”and “recognition” found even in the ants.

When he addresses the more complex mental properties that specifically had been considered by a long tradition of discussion to be the distinctive human properties—possession of language, reason, abstract conceptual thinking, self-reflection—these again are treated as having their manifestations in other forms of life, with none of them unique to human beings. Language, the property that Descartes, for example, had considered to be the primary distinguishing character denoting the human possession of mind as distinct from matter, Darwin treats a developing in a gradual process from animal sounds that parallel the differentiation of species, illustrated by the fact that languages “like organic beings, can be classed in groups under groups” (Darwin 1871 [1981], 60). He closes his discussion of mental powers with an analysis of religious belief that derives it from imagination and belief in spirits found in aboriginal peoples. It can even be homologized with the “deep love of a dog for his master, associated with complete submissions, some fear, and perhaps other feelings” (ibid., 68). Darwin’s discussions of the relation of human and animal mental and emotional properties would set the agenda for a complex discussion that would carry into contemporary debates over animal cognition and the relations of human and animal properties (see the entries on animal cognition ; methods in comparative cognition ; and animal consciousness ).

The subsequent treatment of ethical issues in the third chapter of the Descent was for Darwin a topic to be approached “exclusively from the side of natural history” (ibid., 71). This issue also presented him with some of his most difficult conceptual problems (CD to Gray, 15 March 1870, Burkhardt, Correspondence 18, 68). In this discussion he also employs natural selection theory as an explanatory cause.

Under the heading of “Moral Sense”, Darwin offered some innovations in ethics that do not easily map on to standard ethical positions classified around the familiar categories of Rule or Act Utilitarianism, Kantian Deontology, Hedonism, and Emotivism. Darwin’s closest historical affinities are with the Scottish “Moral Sense” tradition of Frances Hutcheson (1694–1746), Adam Smith (1723?–1790), and David Hume (1711–1776). More immediately Darwin drew from the expositions of the moral sense theory by his distant relative, Sir James Macintosh (1765–1832) (R. J. Richards 1987, 114–122, 206–219).

Traditional moral sense theory linked ethical behavior to an innate property that was considered to be universal in human beings, although it required education and cultivation to reach its full expression (see the entry on moral sentimentalism ). This inherent property, or “moral” sense, presumably explained such phenomena as ethical conscience, the sense of moral duty, and it accounted for altruistic actions that could not be reduced to hedonic seeking of pleasure and avoiding pain. It also did not involve the rational calculation of advantage, or the maximization of greatest happiness by an individual prior to action, as implied by Utilitarianism. For this reason Darwin criticized John Stuart Mill’s version of Utilitarian theory because it relied on acquired habits and the calculation of advantage (Darwin 1871 [1981], 71n5).

Darwin’s reinterpretation of the moral sense tradition within his evolutionary framework also implied important transfomations of this theory of ethics. The moral sense was not to be distinguished from animal instinct but was instead derived historically from the social instincts and developed by natural selection. From this perspective, Darwin could claim a genuine identity of ethical foundations holding between humans and animals, with the precursors of human ethical behavior found in the behavior of other animals, particularly those with social organization. Natural selection then shaped these ethical instincts in ways that favored group survival over immediate individual benefit (ibid., 98). Human ethical behavior is therefore grounded in a natural property developed by natural selection, with the consequence that ethical actions can occur without moral calculus or rational deliberation.

When moral conflict occurs, this is generally attributed to a conflict of instincts, with the stronger of two conflicting instincts favored by natural selection insofar as it favors group benefit (ibid. 84). In human beings the “more enduring Social Instincts” thus come to override the less persistent “individual” instincts.

The adequacy of evolutionary ethical naturalism as a foundation for ethical realism proved to be a point of contention for Darwin’s contemporaries and successors following the publication of the Descent . For some moral philosophers, Darwin had simply reduced ethics to a property subject to the relativizing tendencies of natural selection (Farber 1994: chp. 5). It was, in the view of Darwin’s philosophical critics, to reduce ethics to biology and in doing so, to offer no way to distinguish ethical goods from survival advantages. Not even for some strong supporters of Darwinism, such as Thomas Huxley and Alfred Russel Wallace, was Darwin’s account adequate (ibid., chp. 4). Much of subsequent development of moral philosophy after Darwin would be grounded upon the canonical acceptance of the “is-ought” distinction, which emerged with new force from the critique of “evolutionary” ethical theory. This critique began with Thomas Huxley’s own break with Darwinian ethical theory in his Romanes Lecture, “Evolution and Ethics”of 1893 (Huxley 1893). This lecture, reflecting Huxley’s views eleven years after Darwin’s death, would play an important role in the Chinese reception of Darwinism (Huxley 1895; see above, section 3.1). This line of critique also received an influential academic expression in G. E. Moore’s (1873–1958) Principia Ethica —itself an attack on Spencer’s version of evolutionary ethics (Moore 1903). Debates over the adequacy of evolutionary ethics continue into the present (see the entries on biological altruism and morality and evolutionary biology ; see also, R. J. Richards 2015, 2009, 1999, 1987, Appendix 2; Charmetant 2013; Boniolo and DeAnna (eds.) 2006; Hauser 2006; Katz (ed.) 2000; Maienschein and Ruse (eds.) 1999).

4.4 Reception of the Descent

The international reception of the Descent of Man and Expression of the Emotions is a topic in need of the kind of detailed studies that surround the historical impact of the Origin. These works presented the reading public after 1871 with a more radical and controversial Darwin than had been associated with the author of the popular Journal of Researches or even the Origin itself, and his anthropological works created a watershed in the public reception of Darwin’s views (Radick 2013). The Descent finally made public Darwin’s more radical conclusions about human origins, and seemed to many of his readers, even those previously sympathetic to the Origin , to throw Darwin’s authority behind materialist and anti-religious forces. Public knowledge of Darwin’s own conclusions on human evolution before 1871 had rested on the one vague sentence on the issue in the Origin itself. The Descent made public his more radical conclusions. Even though the question of human evolution had already been dealt with in part by Thomas Huxley in his Man’s Place in Nature of 1863 (Huxley 1863), and by Charles Lyell in the same year in his Geological Evidences of the Antiquity of Man (Lyell 1863), followed by Alfred Russel Wallace’s articles in 1864 and 1870 (Wallace 1864 and online), these authors had either not dealt with the full range of questions presented by the inclusion of human beings in the evolutionary process, or they had emphasized the moral and mental discontinuity between humans and animals. Only Ernst Heinrich Haeckel had drawn out a more general reductive conception of humanity from evolutionary theory and he had not ventured into the specific issues of ethics, social organization, the origins of human races, and the relation of human mental properties to those of animals, all of which are dealt with in the Descent . Darwin’s treatise presented, as one commentator has put it, “a closer resemblance to Darwin’s early naturalistic vision than anything else he ever published” (Durant 1985, 294).

Darwin’s extension of his theory to a range of questions traditionally discussed within philosophy, theology, and social and political theory, has shaped the more general history of Darwinism since the 1870s. It set the agenda for much of the development of psychology of the late nineteenth century (R. J. Richards 1987). It also hardened the opposition of many religiously-based communities against evolutionary theory, although here again, distinctions must be made between different communities (Ellegård 1990, chp. 14). Such opposition was not simply based upon the denial of the literal scriptural account of the origins of humankind, an issue that played out differently within the main religious denominations (Haught 2013; Finnegan 2013; Swetlitz 2013; Artigas, Glick, & Martinez 2006; Moore 1979). The more fundamental opposition was due to the denial of distinctions, other than those of degree, between fundamental human properties and those of animals.

Furthermore, the apparent denial of some kind of divine guidance in the processes behind human evolution and the non-teleological character of Darwin’s final formulations of the natural selection theory in the fifth and sixth editions of the Origin , hardened this opposition. His adoption from Herbert Spencer of designator “survival of the fittest” as a synonym for “natural selection” in the fifth edition of 1869 added to this growing opposition. As a consequence, the favorable readings that many influential religious thinkers—John Henry Newman (1801–1890) is a good example—had given to the original Origin , disappeared. The rhetoric of the Descent , with its conclusion that “man is descended from a hairy quadruped, furnished with a tail and pointed ears” (Darwin 1871 [1981], 389), presented to the public a different Darwin than many had associated with the popular seagoing naturalist.

The new opposition to Darwin is reflected in the many hostile reviews of the Descent to appear in the periodical press (R. J. Richards 1987, 219–230). Particularly at issue were Darwin’s accounts of the origin of ethical principles and intelletual powers, including language, self-reflection, abstract thinking and religious belief as derivations from animal properties (Anon. 1871)

The profound revolution in thought that Darwin created, however, was eventually recognized even by his one-time harsh critics. The once leading British comparative anatomist Richard Owen (1804–1892), who had long been estranged from Darwin since his harsh review of the Origin in 1860, nonetheless could comment on the occasion of Darwin’s burial in Westminster Abbey in a letter to Horace Walpole:

The great value of Darwin’s series of works, summarizing all the evidence of Embryology, Paleontology, & Physiology experimentally applied in producing Varieties of Species, is exemplified in the general acceptance by Biologists of the Secondary Law, by Evolution, of the ‘Origin of Species’ […] In this respect Charles Darwin stands to Biology in the relation which Copernicus stood to Astronomy. […] [Copernicus] knew not how the planets revolved around the sun. To know that required the successive labours of a Galileo, a Kepler and finally a Newton […] Meanwhile our British Copernicus of Biology merits the honour and the gratitude of the Empire, which is manifest by a Statue in Westminster Abbey. (Richard Owen to Horace Walpole, 5 November, 1882, Royal College of Surgeons of England Archives, MS0025/1/5/4).

The subsequent history of the debates surrounding Darwin’s achievement forms a complex story that involves much of the history of life science, as well as ethical theory, psychology, philosophy, theology and social theory since 1870. For a general summary of recent scholarship see Ruse 2013a and articles from this encyclopedia listed below.

This article has intended to give a historical overview of the specific nature of Darwinian theory, and outline the ways in which it differed from the theories of predecessors in the nineteenth century (see the entry evolution before Darwin ). The eventual general consensus achieved by the middle of the twentieth century around the so-named “Synthetic” theory of evolution that would combine population genetics with a mathematical analysis of evolutionary change, has formed a successful research program for more than half a century (Smocovitis 1996; Mayr and Provine 1980; Provine 1971). This “synthesis” has been challenged in recent decades by the current movement known as evolutionary developmental theory, or “evo-devo”. This development represents in some important respects a return to presumably discarded traditions and lines of exploration of the nineteenth and early twentieth centuries which sought to link evolution with embryological development, and to a complex understanding of genetics, with re-examination of the effects of external conditions on inheritance (Gilbert 2015; Newman 2015; Laubichler and Maienschein 2007; Gissis and Jablonka 2011; Pigliucci and Müller 2010; Amundson 2005; Gilbert, Opitz and Raff 1996). Where these debates and revisions in evolutionary theory may lead in another fifty years is a matter of speculation (Gayon 2015 in Sloan, McKenny and Eggleson 2015).

More general philosophical issues associated with evolutionary theory—those surrounding natural teleology, ethics, the relation of evolutionary naturalism to the claims of religious traditions, the implications for the relation of human beings to the rest of the organic world—continue as issues of scholarly inquiry. The status of Darwin’s accounts of human mental powers and moral properties continue to be issues of philosophical debate. The adequacy of his reliance on sexual selection to explain sex and gender roles in human society form heated topics in some feminist scholarship. Such developments suggest that there are still substantial theoretical issues at stake that may alter the future understanding of evolutionary theory in important ways (Sloan, McKenny, & Eggleson [eds] 2015).

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How to cite this entry . Preview the PDF version of this entry at the Friends of the SEP Society . Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO). Enhanced bibliography for this entry at PhilPapers , with links to its database.

• The Complete Works of Charles Darwin Online , maintained by John van Wyhe, Cambridge University Library. In particular note the Darwin Papers & Manuscripts section
• Darwin Manuscripts Project , maintained by David Kohn in cooperation with the American Museum of Natural History Research Library.
• Letter to Charles Lyell, 28 September 1860, DCP-LETT-2931
• Letter from J.D. Hooker, 8 February 1867, DCP-LETT-5395
• Letter to William Turner, 11 February 1867, DCP-LETT-5398
• Letter to Asa Gray, 15 March 1870, DCP-LETT-7132
• Ghiselin, Michael T., 2009, Darwin: A Reader’s Guide [PDF], Occasional Papers of the California Academy of Sciences 155.
• The Huxley File , maintained by Charles Blinderman and David Joyce (Clark University).
• Works by Ernst Heinrich Haeckel , Project Gutenberg.
• Wallace Online , maintained by John van Wyhe, Cambridge University Library.

adaptationism | altruism | altruism: biological | animal: cognition | animal: consciousness | biology: philosophy of | comparative cognition, methods in | creationism | Darwinism | evolution: concept before Darwin | evolution: cultural | fitness | genetics: ecological | life | morality: and evolutionary biology | moral sentimentalism | natural selection | natural selection: units and levels of | Newton, Isaac: philosophy | species | Spencer, Herbert | teleology: teleological notions in biology | Whewell, William

The author wishes to acknowledge the valuable comments on this version of the article by David Depew, Gregory Radick, M. J. S. Hodge, Alan Love, and Xiaoxing Jin. Additional comments were made on an earlier version by Michael Ruse, Robert J. Richards, Edward Zalta, M. Katherine Tillman, and the anonymous reviewers for the Stanford Encyclopedia of Philosophy. I am particularly indebted to Dr. Xiaoxing Jin for information contained in his substantial doctoral work and subsequent research on the reception of Darwinism into China. Responsibility for all interpretations is my own.

Copyright © 2024 by Phillip Sloan < sloan . 1 @ nd . edu >

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The Smithsonian Institution's Human Origins Program

Homo sapiens.

The species that you and all other living human beings on this planet belong to is Homo sapiens . During a time of dramatic climate change 300,000 years ago, Homo sapiens evolved in Africa. Like other early humans that were living at this time, they gathered and hunted food, and evolved behaviors that helped them respond to the challenges of survival in unstable environments.

Anatomically, modern humans can generally be characterized by the lighter build of their skeletons compared to earlier humans. Modern humans have very large brains, which vary in size from population to population and between males and females, but the average size is approximately 1300 cubic centimeters. Housing this big  brain involved the reorganization of the skull into what is thought of as "modern" -- a thin-walled, high vaulted skull with a flat and near vertical forehead. Modern human faces also show much less (if any) of the heavy brow ridges and prognathism of other early humans. Our jaws are also less heavily developed, with smaller teeth.

Scientists sometimes use the term “anatomically modern Homo sapiens” to refer to members of our own species who lived during prehistoric times.

History of Discovery:

Unlike every other human species, Homo sapiens does not have a true type specimen. In other words, there is not a particular Homo sapiens individual that researchers recognize as being the specimen that gave Homo sapiens its name. Even though Linnaeus first described our species in 1758, it was not customary at that time to designate type specimens. It is rumored that in 1994 paleontologist Robert Bakker formally declared the skull of Edward Drinker Cope as the “lectotype”, a specimen essentially serving as the type specimen. When Cope, himself a great paleontologist, died in 1897, he willed his remains to science, and they are held by the University of Pennsylvania. But a type specimen must be one examined by the original author who names a species, so Cope’s remains do not qualify.

How They Survived:

Prehistoric Homo sapiens not only made and used stone tools, they also specialized them and made a variety of smaller, more complex, refined and specialized tools including composite stone tools, fishhooks and harpoons, bows and arrows, spear throwers and sewing needles.

For millions of years all humans, early and modern alike, had to find their own food. They spent a large part of each day gathering plants and hunting or scavenging animals. By 164,000 years ago modern humans were collecting and cooking shellfish and by 90,000 years ago modern humans had begun making special fishing tools. Then, within just the past 12,000 years, our species, Homo sapiens , made the transition to producing food and changing our surroundings. Humans found they could control the growth and breeding of certain plants and animals. This discovery led to farming and herding animals, activities that transformed Earth’s natural landscapes—first locally, then globally. As humans invested more time in producing food, they settled down. Villages became towns, and towns became cities. With more food available, the human population began to increase dramatically. Our species had been so successful that it has inadvertently created a turning point in the history of life on Earth.

Modern humans evolved a unique combination of physical and behavioral characteristics, many of which other early human species also possessed, though not to the same degree. The complex brains of modern humans enabled them to interact with each other and with their surroundings in new and different ways. As the environment became more unpredictable, bigger brains helped our ancestors survive. They made specialized tools, and use tools to make other tools, as described above; they ate a variety of animal and plant foods; they had control over fire; they lived in shelters; they built broad social networks, sometimes including people they have never even met; they exchanged resources over wide areas; and they created art, music, personal adornment, rituals, and a complex symbolic world. Modern humans have spread to every continent and vastly expanded their numbers. They have altered the world in ways that benefit them greatly. But this transformation has unintended consequences for other species as well as for ourselves, creating new survival challenges.

Evolutionary Tree Information:

Fossils and DNA confirm humans are one of more than 200 species belonging to the order of Primates. Within that larger group, humans are nested within the great ape family. Although we did not evolve from any of the apes living today, we share characteristics with chimpanzees, gorillas, and orangutans (the great apes), as well as other apes. We most likely evolved from Homo heidelbergensis , the common ancestor we share with Neanderthals, who are our closest extinct relatives.

We don’t know everything about our own species—but we keep learning more! Through studies of fossils, genetics, behavior, and biology of modern humans, we continue to learn more about who we are.

Below are some of the still unanswered questions about  Homo sapiens  that may be answered with future discoveries:

• Who was our direct evolutionary ancestor? Was it Homo heidelbergensis, like many paleoanthropologists think, or another species?
• How much interbreeding occured between our species and  Homo neanderthalensis?
• What does the future hold for our species in an evolutionary sense? 

References:

Recommended readings:

McBrearty, S., Brooks, A., 2000. The revolution that wasn't: a new interpretation of the origin of modern humans. Journal of Human Evolution 39, 453-563.

Henshilwood, C.S., Marean, C.W., 2003. The origin of modern human behavior: critique of the models and their test implications. Current Anthropology 44, 627-651.

Ngaloba LH 18

Skhūl V was recovered from the Skhūl Cave near Mount Carmel, Israel, along with the skeletons of nine other adults and children. Some anatomical features, like the brow ridges and occipital bun of the male Skhūl V skull are reminiscent of earlier humans; however, Skhūl V also has the high, vertical forehead and rounded skull typical of modern human skulls.

Cro-Magnon 1

Cro-Magnon 1 is a middle-aged, male skeleton of one of the first modern human fossils ever found, at Cro-Magnon, France in 1868. Scientists estimate his age at death at less than 50 years old. Except for the teeth, his skull is complete, though the bones in his face are noticeably pitted from a fungal infection.

Lapa Vermelha IV Hominid 1

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Science | February 2, 2021

An Evolutionary Timeline of Homo Sapiens

Scientists share the findings that helped them pinpoint key moments in the rise of our species

Brian Handwerk

Science Correspondent

The long evolutionary journey that created modern humans began with a single step—or more accurately—with the ability to walk on two legs. One of our earliest-known ancestors, Sahelanthropus , began the slow transition from ape-like movement some six million years ago, but Homo sapiens wouldn’t show up for more than five million years. During that long interim, a menagerie of different human species lived, evolved and died out, intermingling and sometimes interbreeding along the way. As time went on, their bodies changed, as did their brains and their ability to think, as seen in their tools and technologies.

To understand how Homo sapiens eventually evolved from these older lineages of hominins, the group including modern humans and our closest extinct relatives and ancestors, scientists are unearthing ancient bones and stone tools, digging into our genes and recreating the changing environments that helped shape our ancestors’ world and guide their evolution.

These lines of evidence increasingly indicate that H. sapiens originated in Africa, although not necessarily in a single time and place. Instead it seems diverse groups of human ancestors lived in habitable regions around Africa, evolving physically and culturally in relative isolation, until climate driven changes to African landscapes spurred them to intermittently mix and swap everything from genes to tool techniques. Eventually, this process gave rise to the unique genetic makeup of modern humans.

“East Africa was a setting in foment—one conducive to migrations across Africa during the period when Homo sapiens arose,” says Rick Potts , director of the Smithsonian’s Human Origins Program. “It seems to have been an ideal setting for the mixing of genes from migrating populations widely spread across the continent. The implication is that the human genome arose in Africa. Everyone is African, and yet not from any one part of Africa.”

New discoveries are always adding key waypoints to the chart of our human journey. This timeline of Homo sapiens features some of the best evidence documenting how we evolved.

550,000 to 750,000 Years Ago: The Beginning of the Homo sapiens Lineage

Genes, rather than fossils, can help us chart the migrations, movements and evolution of our own species—and those we descended from or interbred with over the ages.

The oldest-recovered DNA of an early human relative comes from Sima de los Huesos , the “Pit of Bones.” At the bottom of a cave in Spain’s Atapuerca Mountains scientists found thousands of teeth and bones from 28 different individuals who somehow ended up collected en masse. In 2016, scientists painstakingly teased out the partial genome from these 430,000-year-old remains to reveal that the humans in the pit are the oldest known Neanderthals , our very successful and most familiar close relatives. Scientists used the molecular clock to estimate how long it took to accumulate the differences between this oldest Neanderthal genome and that of modern humans, and the researchers suggest that a common ancestor lived sometime between 550,000 and 750,000 years ago.

Pinpoint dating isn't the strength of genetic analyses, as the 200,000-year margin of error shows. “In general, estimating ages with genetics is imprecise,” says Joshua Akey, who studies evolution of the human genome at Princeton University. “Genetics is really good at telling us qualitative things about the order of events, and relative time frames.” Before genetics, these divergence dates were estimated by the oldest fossils of various lineages scientists found. In the case of H. sapiens, known remains only date back some 300,000 years, so gene studies have located the divergence far more accurately on our evolutionary timeline than bones alone ever could.

Though our genes clearly show that modern humans, Neanderthals and Denisovans —a mysterious hominin species that left behind substantial traces in our DNA but, so far, only a handful of tooth and bone remains—do share a common ancestor, it’s not apparent who it was. Homo heidelbergensis , a species that existed from 200,000 to 700,000 years ago, is a popular candidate. It appears that the African family tree of this species leads to Homo sapiens while a European branch leads to Homo neanderthalensis and the Denisovans.

More ancient DNA could help provide a clearer picture, but finding it is no sure bet. Unfortunately, the cold, dry and stable conditions best for long-term preservation aren’t common in Africa, and few ancient African human genomes have been sequenced that are older than 10,000 years.

“We currently have no ancient DNA from Africa that even comes near the timeframes of our evolution—a process that is likely to have largely taken place between 800,000 and 300,000 years ago,” says Eleanor Scerri, an archaeological scientist at the Max Planck Institute for the Science of Human History in Germany.

300,000 Years Ago: Fossils Found of Oldest Homo sapiens

As the physical remains of actual ancient people, fossils tell us most about what they were like in life. But bones or teeth are still subject to a significant amount of interpretation. While human remains can survive after hundreds of thousands of years, scientists can’t always make sense of the wide range of morphological features they see to definitively classify the remains as Homo sapiens , or as different species of human relatives.

Fossils often boast a mixture of modern and primitive features, and those don’t evolve uniformly toward our modern anatomy. Instead, certain features seem to change in different places and times, suggesting separate clusters of anatomical evolution would have produced quite different looking people.

No scientists suggest that Homo sapiens first lived in what’s now Morocco, because so much early evidence for our species has been found in both South Africa and East Africa. But fragments of 300,000-year-old skulls, jaws, teeth and other fossils found at Jebel Irhoud , a rich site also home to advanced stone tools, are the oldest Homo sapiens remains yet found.

The remains of five individuals at Jebel Irhoud exhibit traits of a face that looks compellingly modern, mixed with other traits like an elongated brain case reminiscent of more archaic humans. The remains’ presence in the northwestern corner of Africa isn’t evidence of our origin point, but rather of how widely spread humans were across Africa even at this early date.

Other very old fossils often classified as early Homo sapiens come from Florisbad, South Africa (around 260,000 years old), and the Kibish Formation along Ethiopia’s Omo River (around 195,000 years old).

The 160,000-year-old skulls of two adults and a child at Herto, Ethiopia, were classified as the subspecies Homo sapiens idaltu because of slight morphological differences including larger size. But they are otherwise so similar to modern humans that some argue they aren’t a subspecies at all. A skull discovered at Ngaloba, Tanzania, also considered Homo sapiens , represents a 120,000-year-old individual with a mix of archaic traits and more modern aspects like smaller facial features and a further reduced brow.

Debate over the definition of which fossil remains represent modern humans, given these disparities, is common among experts. So much so that some seek to simplify the characterization by considering them part of a single, diverse group.

“The fact of the matter is that all fossils before about 40,000 to 100,000 years ago contain different combinations of so called archaic and modern features. It’s therefore impossible to pick and choose which of the older fossils are members of our lineage or evolutionary dead ends,” Scerri suggests. “The best model is currently one in which they are all early Homo sapiens , as their material culture also indicates.”

As Scerri references, African material culture shows a widespread shift some 300,000 years ago from clunky, handheld stone tools to the more refined blades and projectile points known as Middle Stone Age toolkits.

So when did fossils finally first show fully modern humans with all representative features? It’s not an easy answer. One skull (but only one of several) from Omo Kibish looks much like a modern human at 195,000 years old, while another found in Nigeria’s Iwo Eleru cave, appears very archaic, but is only 13,000 years old . These discrepancies illustrate that the process wasn’t linear, reaching some single point after which all people were modern humans.

300,000 Years Ago: Artifacts Show a Revolution in Tools

Our ancestors used stone tools as long as 3.3 million years ago and by 1.75 million years ago they’d adopted the Acheulean culture , a suite of chunky handaxes and other cutting implements that remained in vogue for nearly 1.5 million years. As recently as 400,000 years ago, thrusting spears used during the hunt of large prey in what is now Germany were state of the art. But they could only be used up close, an obvious and sometimes dangerous limitation.

Even as they acquired the more modern anatomy seen in living humans, the ways our ancestors lived, and the tools they created, changed as well.

Humans took a leap in tool tech with the Middle Stone Age some 300,000 years ago by making those finely crafted tools with flaked points and attaching them to handles and spear shafts to greatly improve hunting prowess. Projectile points like those Potts and colleagues dated to 298,000 to 320,000 years old in southern Kenya were an innovation that suddenly made it possible to kill all manner of elusive or dangerous prey. “It ultimately changed how these earliest sapiens interacted with their ecosystems, and with other people,” says Potts.

Scrapers and awls, which could be used to work animal hides for clothing and to shave wood and other materials, appeared around this time. By at least 90,000 years ago barbed points made of bone— like those discovered at Katanda, Democratic Republic of the Congo —were used to spearfish

As with fossils, tool advancements appear in different places and times, suggesting that distinct groups of people evolved, and possibly later shared, these tool technologies. Those groups may include other humans who are not part of our own lineage.

Last year a collection including sophisticated stone blades was discovered near Chennai, India , and dated to at least 250,000 years ago. The presence of this toolkit in India so soon after modern humans appeared in Africa suggests that other species may have also invented them independently—or that some modern humans spread the technology by leaving Africa earlier than most current thinking suggests.

100,000 to 210,000 Years Ago: Fossils Show Homo sapiens Lived Outside of Africa

Many genetic analyses tracing our roots back to Africa make it clear that Homo sapiens originated on that continent. But it appears that we had a tendency to wander from a much earlier era than scientists had previously suspected.

A jawbone found inside a collapsed cave on the slopes of Mount Carmel, Israel, reveals that modern humans dwelt there, alongside the Mediterranean, some 177,000 to 194,000 years ago. Not only are the jaw and teeth from Misliya Cave unambiguously similar to those seen in modern humans, they were found with sophisticated handaxes and flint tools.

Other finds in the region, including multiple individuals at Qafzeh, Israel, are dated later. They range from 100,000 to 130,000 years ago, suggesting a long presence for humans in the region. At Qafzeh, human remains were found with pieces of red ocher and ocher-stained tools in a site that has been interpreted as the oldest intentional human burial .

Among the limestone cave systems of southern China, more evidence has turned up from between 80,000 and 120,000 years ago. A 100,000-year-old jawbone, complete with a pair of teeth, from Zhirendong retains some archaic traits like a less prominent chin, but otherwise appears so modern that it may represent Homo sapiens . A cave at Daoxian yielded a surprising array of ancient teeth , barely distinguishable from our own, which suggest that Homo sapiens groups were already living very far from Africa from 80,000 to 120,000 years ago.

Even earlier migrations are possible; some believe evidence exists of humans reaching Europe as long as 210,000 years ago. While most early human finds spark some scholarly debate, few reach the level of the Apidima skull fragment, in southern Greece, which may be more than 200,000 years old and might possibly represent the earliest modern human fossil discovered outside of Africa. The site is steeped in controversy , however, with some scholars believing that the badly preserved remains look less those of our own species and more like Neanderthals, whose remains are found just a few feet away in the same cave. Others question the accuracy of the dating analysis undertaken at the site, which is tricky because the fossils have long since fallen out of the geological layers in which they were deposited.

While various groups of humans lived outside of Africa during this era, ultimately, they aren’t part of our own evolutionary story. Genetics can reveal which groups of people were our distant ancestors and which had descendants who eventually died out.

“Of course, there could be multiple out of Africa dispersals,” says Akey. “The question is whether they contributed ancestry to present day individuals and we can say pretty definitely now that they did not.”

50,000 to 60,000 Years Ago: Genes and Climate Reconstructions Show a Migration Out of Africa

All living non-Africans, from Europeans to Australia’s aboriginal people, can trace most of their ancestry to humans who were part of a landmark migration out of Africa beginning some 50,000 to 60,000 years ago , according to numerous genetic studies published in recent years. Reconstructions of climate suggest that lower sea levels created several advantageous periods for humans to leave Africa for the Arabian Peninsula and the Middle East, including one about 55,000 years ago.

“Just by looking at DNA from present day individuals we’ve been able to infer a pretty good outline of human history,” Akey says. “A group dispersed out of Africa maybe 50 to 60 thousand years ago, and then that group traveled around the world and eventually made it to all habitable places of the world.”

While earlier African emigres to the Middle East or China may have interbred with some of the more archaic hominids still living at that time, their lineage appears to have faded out or been overwhelmed by the later migration.

15,000 to 40,000 Years Ago: Genetics and Fossils Show Homo sapiens Became the Only Surviving Human Species

For most of our history on this planet, Homo sapiens have not been the only humans. We coexisted, and as our genes make clear frequently interbred with various hominin species, including some we haven’t yet identified. But they dropped off, one by one, leaving our own species to represent all humanity. On an evolutionary timescale, some of these species vanished only recently.

On the Indonesian island of Flores, fossils evidence a curious and diminutive early human species nicknamed “hobbit.” Homo floresiensis appear to have been living until perhaps 50,000 years ago, but what happened to them is a mystery. They don’t appear to have any close relation to modern humans including the Rampasasa pygmy group, which lives in the same region today.

Neanderthals once stretched across Eurasia from Portugal and the British Isles to Siberia. As Homo sapiens became more prevalent across these areas the Neanderthals faded in their turn, being generally consigned to history by some 40,000 years ago. Some evidence suggests that a few die-hards might have held on in enclaves, like Gibraltar, until perhaps 29,000 years ago. Even today traces of them remain because modern humans carry Neanderthal DNA in their genome .

Our more mysterious cousins, the Denisovans, left behind so few identifiable fossils that scientists aren’t exactly sure what they looked like, or if they might have been more than one species. A recent study of human genomes in Papua New Guinea suggests that humans may have lived with and interbred with Denisovans there as recently as 15,000 years ago, though the claims are controversial. Their genetic legacy is more certain. Many living Asian people inherited perhaps 3 to 5 percent of their DNA from the Denisovans.

Despite the bits of genetic ancestry they contributed to living people, all of our close relatives eventually died out, leaving Homo sapiens as the only human species. Their extinctions add one more intriguing, perhaps unanswerable question to the story of our evolution—why were we the only humans to survive?

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Brian Handwerk | READ MORE

Brian Handwerk is a science correspondent based in Amherst, New Hampshire.

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Homo sapiens

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• Smithsonian National Museum of Natiral History - Human Evolution Evidence - Homo Sapien
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Homo sapiens , the species to which all modern human beings belong. Homo sapiens is one of several species grouped into the genus Homo , but it is the only one that is not extinct . See also human evolution .

The name Homo sapiens was applied in 1758 by the father of modern biological classification ( see taxonomy ), Carolus Linnaeus . It had long been known that human beings physically resemble the primates more closely than any other known living organisms, but at the time it was a daring act to classify human beings within the same framework used for the rest of nature. Linnaeus, concerned exclusively with similarities in bodily structure, faced only the problem of distinguishing H. sapiens from apes ( gorillas , chimpanzees , orangutans , and gibbons ), which differ from humans in numerous bodily as well as cognitive features. ( Charles Darwin’s treatise on evolution , On the Origin of Species , would come 101 years later.)

(Read Ray Kurzweil’sBritannica essay on the future of “Nonbiological Man.”)

Since Linnaeus’s time, a large fossil record has been discovered. This record contains numerous extinct species that are much more closely related to humans than to today’s apes and that were presumably more similar to H. sapiens behaviorally as well. Following the ancestors of modern human beings into the distant past raises the question of what is meant by the word human . H. sapiens is human by definition, whereas apes are not. But what of the extinct members of the human tribe ( Hominini ), who were clearly not H. sapiens but were nonetheless very much like them? There is no definitive answer to this question. Although human evolution can be said to involve all those species more closely related to H. sapiens than to the apes, the adjective human is usually applied only to H. sapiens and other members of the genus Homo (e.g., H. erectus , H. habilis ). Behaviorally, only H. sapiens can be said to be “fully human,” but even the definition of H. sapiens is a matter of active debate. Some paleoanthropologists extend the span of this species far back into time to include many anatomically distinctive fossils that others prefer to allocate to several different extinct species. In contrast, a majority of paleoanthropologists, wishing to bring the study of hominins into line with that of other mammals , prefer to assign to H. sapiens only those fossil forms that fall within the anatomic spectrum of the species as it exists today. In this sense, H. sapiens is very recent, having originated in Africa more than 315,000 years ago (315 kya).

(Read Yuval Noah Harari’s Britannica essay on the future of “Nonconscious Man.”)

Before about 1980 it was widely thought that distinctively hominin fossils could be identified from 14 to 12 million years ago (mya). However, during the 1970s geneticists introduced the use of molecular clocks to calculate how long species had been separated from a common ancestor. The molecular clock concept is based on an assumed regularity in the accumulation of tiny changes in the genetic codes of humans and other organisms. Use of this concept, together with a reanalysis of the fossil record , moved the estimated time of the evolutionary split between apes and human ancestors forward to as recently as about 5 mya. Since then the molecular data emerging from DNA sequencing and a steady trickle of new hominin fossil finds have pushed the earliest putative hominin ancestry back in time somewhat, to perhaps 8–6 mya.

Introductory essay

Written by the educator who created What Makes Us Human?, a brief look at the key facts, tough questions and big ideas in his field. Begin this TED Study with a fascinating read that gives context and clarity to the material.

As a biological anthropologist, I never liked drawing sharp distinctions between human and non-human. Such boundaries make little evolutionary sense, as they ignore or grossly underestimate what we humans have in common with our ancestors and other primates. What's more, it's impossible to make sharp distinctions between human and non-human in the paleoanthropological record. Even with a time machine, we couldn't go back to identify one generation of humans and say that the previous generation contained none: one's biological parents, by definition, must be in the same species as their offspring. This notion of continuity is inherent to most evolutionary perspectives and it's reflected in the similarities (homologies) shared among very different species. As a result, I've always been more interested in what makes us similar to, not different from, non-humans.

Evolutionary research has clearly revealed that we share great biological continuity with others in the animal kingdom. Yet humans are truly unique in ways that have not only shaped our own evolution, but have altered the entire planet. Despite great continuity and similarity with our fellow primates, our biocultural evolution has produced significant, profound discontinuities in how we interact with each other and in our environment, where no precedent exists in other animals. Although we share similar underlying evolved traits with other species, we also display uses of those traits that are so novel and extraordinary that they often make us forget about our commonalities. Preparing a twig to fish for termites may seem comparable to preparing a stone to produce a sharp flake—but landing on the moon and being able to return to tell the story is truly out of this non-human world.

Humans are the sole hominin species in existence today. Thus, it's easier than it would have been in the ancient past to distinguish ourselves from our closest living relatives in the animal kingdom. Primatologists such as Jane Goodall and Frans de Waal, however, continue to clarify why the lines dividing human from non-human aren't as distinct as we might think. Goodall's classic observations of chimpanzee behaviors like tool use, warfare and even cannibalism demolished once-cherished views of what separates us from other primates. de Waal has done exceptional work illustrating some continuity in reciprocity and fairness, and in empathy and compassion, with other species. With evolution, it seems, we are always standing on the shoulders of others, our common ancestors.

Primatology—the study of living primates—is only one of several approaches that biological anthropologists use to understand what makes us human. Two others, paleoanthropology (which studies human origins through the fossil record) and molecular anthropology (which studies human origins through genetic analysis), also yield some surprising insights about our hominin relatives. For example, Zeresenay Alemsegad's painstaking field work and analysis of Selam, a 3.3 million-year old fossil of a 3-year-old australopithecine infant from Ethiopia, exemplifies how paleoanthropologists can blur boundaries between living humans and apes.

Selam, if alive today, would not be confused with a three-year-old human—but neither would we mistake her for a living ape. Selam's chimpanzee-like hyoid bone suggests a more ape-like form of vocal communication, rather than human language capability. Overall, she would look chimp-like in many respects—until she walked past you on two feet. In addition, based on Selam's brain development, Alemseged theorizes that Selam and her contemporaries experienced a human-like extended childhood with a complex social organization.

Fast-forward to the time when Neanderthals lived, about 130,000 – 30,000 years ago, and most paleoanthropologists would agree that language capacity among the Neanderthals was far more human-like than ape-like; in the Neanderthal fossil record, hyoids and other possible evidence of language can be found. Moreover, paleogeneticist Svante Pääbo's groundbreaking research in molecular anthropology strongly suggests that Neanderthals interbred with modern humans. Paabo's work informs our genetic understanding of relationships to ancient hominins in ways that one could hardly imagine not long ago—by extracting and comparing DNA from fossils comprised largely of rock in the shape of bones and teeth—and emphasizes the great biological continuity we see, not only within our own species, but with other hominins sometimes classified as different species.

Though genetics has made truly astounding and vital contributions toward biological anthropology by this work, it's important to acknowledge the equally pivotal role paleoanthropology continues to play in its tandem effort to flesh out humanity's roots. Paleoanthropologists like Alemsegad draw on every available source of information to both physically reconstruct hominin bodies and, perhaps more importantly, develop our understanding of how they may have lived, communicated, sustained themselves, and interacted with their environment and with each other. The work of Pääbo and others in his field offers powerful affirmations of paleoanthropological studies that have long investigated the contributions of Neanderthals and other hominins to the lineage of modern humans. Importantly, without paleoanthropology, the continued discovery and recovery of fossil specimens to later undergo genetic analysis would be greatly diminished.

Molecular anthropology and paleoanthropology, though often at odds with each other in the past regarding modern human evolution, now seem to be working together to chip away at theories that portray Neanderthals as inferior offshoots of humanity. Molecular anthropologists and paleoanthropologists also concur that that human evolution did not occur in ladder-like form, with one species leading to the next. Instead, the fossil evidence clearly reveals an evolutionary bush, with numerous hominin species existing at the same time and interacting through migration, some leading to modern humans and others going extinct.

Molecular anthropologist Spencer Wells uses DNA analysis to understand how our biological diversity correlates with ancient migration patterns from Africa into other continents. The study of our genetic evolution reveals that as humans migrated from Africa to all continents of the globe, they developed biological and cultural adaptations that allowed for survival in a variety of new environments. One example is skin color. Biological anthropologist Nina Jablonski uses satellite data to investigate the evolution of skin color, an aspect of human biological variation carrying tremendous social consequences. Jablonski underscores the importance of trying to understand skin color as a single trait affected by natural selection with its own evolutionary history and pressures, not as a tool to grouping humans into artificial races.

For Pääbo, Wells, Jablonski and others, technology affords the chance to investigate our origins in exciting new ways, adding pieces into the human puzzle at a record pace. At the same time, our technologies may well be changing who we are as a species and propelling us into an era of "neo-evolution."

Increasingly over time, human adaptations have been less related to predators, resources, or natural disasters, and more related to environmental and social pressures produced by other humans. Indeed, biological anthropologists have no choice but to consider the cultural components related to human evolutionary changes over time. Hominins have been constructing their own niches for a very long time, and when we make significant changes (such as agricultural subsistence), we must adapt to those changes. Classic examples of this include increases in sickle-cell anemia in new malarial environments, and greater lactose tolerance in regions with a long history of dairy farming.

Today we can, in some ways, evolve ourselves. We can enact biological change through genetic engineering, which operates at an astonishing pace in comparison to natural selection. Medical ethicist Harvey Fineberg calls this "neo-evolution". Fineberg goes beyond asking who we are as a species, to ask who we want to become and what genes we want our offspring to inherit. Depending on one's point of view, the future he envisions is both tantalizing and frightening: to some, it shows the promise of science to eradicate genetic abnormalities, while for others it raises the specter of eugenics. It's also worth remembering that while we may have the potential to influence certain genetic predispositions, changes in genotypes do not guarantee the desired results. Environmental and social pressures like pollution, nutrition or discrimination can trigger "epigenetic" changes which can turn genes on or off, or make them less or more active. This is important to factor in as we consider possible medical benefits from efforts in self-directed evolution. We must also ask: In an era of human-engineered, rapid-rate neo-evolution, who decides what the new human blueprints should be?

Technology figures in our evolutionary future in other ways as well. According to anthropologist Amber Case, many of our modern technologies are changing us into cyborgs: our smart phones, tablets and other tools are "exogenous components" that afford us astonishing and unsettling capabilities. They allow us to travel instantly through time and space and to create second, "digital selves" that represent our "analog selves" and interact with others in virtual environments. This has psychological implications for our analog selves that worry Case: a loss of mental reflection, the "ambient intimacy" of knowing that we can connect to anyone we want to at any time, and the "panic architecture" of managing endless information across multiple devices in virtual and real-world environments.

Despite her concerns, Case believes that our technological future is essentially positive. She suggests that at a fundamental level, much of this technology is focused on the basic concerns all humans share: who am I, where and how do I fit in, what do others think of me, who can I trust, who should I fear? Indeed, I would argue that we've evolved to be obsessed with what other humans are thinking—to be mind-readers in a sense—in a way that most would agree is uniquely human. For even though a baboon can assess those baboons it fears and those it can dominate, it cannot say something to a second baboon about a third baboon in order to trick that baboon into telling a fourth baboon to gang up on a fifth baboon. I think Facebook is a brilliant example of tapping into our evolved human psychology. We can have friends we've never met and let them know who we think we are—while we hope they like us and we try to assess what they're actually thinking and if they can be trusted. It's as if technology has provided an online supply of an addictive drug for a social mind evolved to crave that specific stimulant!

Yet our heightened concern for fairness in reciprocal relationships, in combination with our elevated sense of empathy and compassion, have led to something far greater than online chats: humanism itself. As Jane Goodall notes, chimps and baboons cannot rally together to save themselves from extinction; instead, they must rely on what she references as the "indomitable human spirit" to lessen harm done to the planet and all the living things that share it. As Goodall and other TED speakers in this course ask: will we use our highly evolved capabilities to secure a better future for ourselves and other species?

I hope those reading this essay, watching the TED Talks, and further exploring evolutionary perspectives on what makes us human, will view the continuities and discontinuities of our species as cause for celebration and less discrimination. Our social dependency and our prosocial need to identify ourselves, our friends, and our foes make us human. As a species, we clearly have major relationship problems, ranging from personal to global scales. Yet whenever we expand our levels of compassion and understanding, whenever we increase our feelings of empathy across cultural and even species boundaries, we benefit individually and as a species.

Get started

Zeresenay Alemseged

The search for humanity's roots, relevant talks.

We are all cyborgs now

Frans de Waal

Moral behavior in animals.

Harvey Fineberg

Are we ready for neo-evolution.

Jane Goodall

What separates us from chimpanzees.

Nina Jablonski

Skin color is an illusion.

Spencer Wells

A family tree for humanity.

Svante Pääbo

Dna clues to our inner neanderthal.

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Essay on Human Evolution: Top 6 Essays | Biology

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Here is a compilation of essays on ‘Human Evolution’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Human Evolution’ especially written for school and college students.

Essay on Human Evolution

Essay Contents:

• Essay on the Models of Human Evolution

Essay # 1.   Introduction to Human Evolution:

Evolution as a process is composed of two parts:

1. An organism reproducing mechanism that provides variable organisms. Changes to the organism are largely random and effect future generations. They are made without regard to consequences to the organism.

2. A changing environment which screens organism changes. The environment provides stress on the variable organisms that selectively allows, through competition, certain changes to become dominant and certain others to be eliminated, without consideration for the future of the mechanism.

That same process provides mechanism (organism) disintegration if a strong screening environment is not present. Evolution is a two-way process which does not always work to the long term advantage of the organism and in fact often becomes quite deadly to a given species and thereby eradicates it.

The evolutionary process is bidirectional in its effect. It may, depending on the environment, either improve a given characteristic or decay it. Since the first step in the process is largely random and most organisms are quite complex, almost all of the variations are harmful.

A characteristic of a species advances if the environment is harsh, since most harmful variations to that characteristic will be eliminated through death and suffering at a rapid rate, leaving only the inconsequential and helpful changes in the lineage.

If the environment is benign with respect to the capability of the species then the harmful changes are not eliminated and the species will degenerate to a point of balance with the environment.

Human evolution is the part of biological evolution concerning the emergence of Homo sapiens as a distinct species from other hominans, great apes and placental mammals. It is the subject of a broad scientific inquiry that seeks to understand and describe how this change occurred.

Mammals developed from primitive mammal-like reptiles during the Triassic Period, some 200-245 million years ago. After the terminal Cretaceous extinction (65 million years ago) eliminated the dinosaurs, mammals as one of the surviving groups, underwent an adaptive radiation during the Tertiary Period.

The major orders of mammals developed at this time, including the Primates to which humans belong. Other primates include the tarsiers, lemurs, gibbons, monkeys, and apes. Although we have significant differences from other primates, we share an evolutionary history that includes traits such as opposable thumbs, stereoscopic vision, larger brains, and nails replacing claws.

Primates are relatively unspecialized mammals- they have no wings, still have all four limbs, cannot run very fast, have generally weak teeth, and lack armor or thick protective hides. However, the combination of primate adaptations that include larger brains, tool use, social structure, stereoscopic color vision, highly developed forelimbs and hands, versatile teeth, and upright posture, place them among the most advanced mammals.

Approximately 20 million years ago central and east Africa was densely forested. Climatic changes resulting from plate tectonic movements and episodes of global cooling about 15 million years ago caused a replacement of the forest by a drier-adapted savanna mixed with open areas of forest. During the course of hominid evolution, periodic climate changes would trigger bursts of evolution and/or extinction.

Primates have modifications to their ulna and radius (bones of the lower arm) allowing them to turn their hand without turning their elbow. Many primates can also swivel or turn their arms at the shoulder. These two adaptations offer advantages to life in the trees.

Primates have five digits on their forelimbs. They are able to grasp objects with their forelimbs in what is known as a prehensile movement. A second modification makes one of the digits opposable, allowing the tips of the fingers and thumb to touch.

Placement of the eyes on the front of the head increases depth perception, an advantageous trait in tree-dwelling primates. Changes in the location of rods and cones in the eye adapted primates for color vision as well as peripheral vision in dim light.

Upright posture allows a primate to view its surroundings as well as to use its hands for some other task. Hominids, the lineage leading to humans, had changes in the shape and size of their pelvis, femur, and knees that allowed bipedalism (walking on two legs). The change from quadruped to biped happened in stages, culminating in humans, who can walk or run on two legs.

Several trends of primate evolution are evident in the teeth and jaw. First, change in the geometry of the jaw reduced the snout into a flat face. Second, changes in tooth arrangement and numbers increased the efficiency of those teeth for grinding food. Third, about 1.5 million years ago our diet changed from fruits and vegetables to include meat.

Essay # 2. Origin of Apes and Hominids:

The fossil record indicates primates evolved about approximately 30 million years ago in Africa. One branch of primates evolved into the Old and New World Monkeys, the other into the hominoids (the line of descent common to both apes and man).

Fossil hominoids occur in Africa during the Miocene epoch of the Tertiary period. They gave rise to an array of species in response to major climate fluxes in their habitats. However, the nature of those habitats leads to an obscuration of the line that leads to humans (the hominids).

Until a few years ago, the ramapiths were thought to have given rise to the hominids. We now consider ramapiths ancestral to the orangutang. The hominid line arose from some as-yet-unknown ancestor. Lacking fossil evidence, biochemical and DNA evidence suggests a split of the hominid from hominoid line about 6 to 8 million years ago.

Australopithecus afarensis, the first of the human-like hominids we know of, first appeared about 3.6-4 million years ago. This species had a combination of human (bipedalism) and apelike features (short legs and relatively long arms). The arm bones were curved like chimps, but the elbows were more human-like. Scientists speculate that A. afarensis spent some time climbing trees, as well as on the ground.

Australopithecus ramidus is an older species, about 4.4 million years, and is generally considered more anatomically primitive than A. afarensis. The relationship between the two species remains to be solved.

History of Man:

I. Ardipithicus ramidus- 5 to 4 million years ago

II. Australopithecus anamensis- 4.2 to 3.9 million years ago

III. Australopithecus afarensis- 4 to 2.7 million years ago

IV. Australopithecus africanus- 3 to 2 million years ago

V. Australopithecus robustus- 2.2 to 1.6 million years ago

VI. Homo habilis- 2.2 to 1.6 million years ago

VII. Homo erectus- 2.0 to 0.4 million years ago

VIII. Homo sapiens archaic- 400 to 200 thousand years ago

IX. Homo sapiens neandertalensis- 200 to 30 thousand years ago

X. Homo sapiens sapiens- 200 thousand years ago to present.

The role of A. afarensis as the stem from which the other hominids arose is in some dispute. About 2 million years ago, after a long million year period of little change, as many as six hominid species evolved in response to climate changes associated with the beginning of the Ice Age.

Two groups developed- the australopithecines, generally smaller brained and not users of tools; and the line that led to genus Homo, larger brained and makers and users of tools. The australopithecines died out 1 million years ago; Homo, despite their best efforts (atomic weapons, pollution) is still here!

With an incomplete fossil record, australopithecines, at least the smaller form, A. africanus, was thought ancestral to Homo. Recent discoveries however have caused a reevaluation of that hypothesis. One pattern is sure, human traits evolved at different rates and at different times, in a mosaic- some features (skeletal, dietary) establishing themselves quickly, others developing later (tool making, language, use of fire).

A cluster of species developed about 2-2.5 million years ago in Africa. Homo had a larger brain and a differently shaped skull and teeth than the australopithecines. About 1.8 million years ago, early Homo gave rise to Homo erectus, the species thought to have been ancestral to our own.

Soon after its origin (1.8 million but probably older than 2 million years ago) in Africa, Homo erectus appears to have migrated out of Africa and into Europe and Asia. Homo erectus differed from early species of Homo in having a larger brain size, flatter face, and prominent brow ridges. Homo erectus is similar to modern humans in size, but has some differences in the shape of the skull, a receding chin, brow ridges, and differences in teeth.

Homo erectus was the first hominid to:

1. Provide evidence the social and cultural aspects of human evolution.

2. Leave Africa (living in Africa, Europe, and Asia).

3. Use fire.

4. Have social structures for food gathering.

5. Utilize permanent settlements.

6. Provide a prolonged period of growth and maturation after birth Between 100,000 and 500,000 years ago, the world population of an estimated 1 million Homo erectus disappeared, replaced by a new species, Homo sapiens. How, when and where this new species arose and how it replaced its predecessor remain in doubt. Answering those questions has become a multidisciplinary task.

Two hypotheses differ on how and where Homo sapiens originated:

1. The Out-of-Africa Hypothesis proposes that some H. erectus remained in Africa and continued to evolve into H. sapiens, and left Africa about 100,000-200,000 years ago. From a single source, H. sapiens replaced all populations of H. erectus.

Human populations today are thus all descended from a single speciation event in Africa and should display a high degree of genetic similarity. Support for this hypothesis comes from DNA studies of mitochondria- since African populations display the greatest diversity of mitochondrial DNA, modern humans have been in Africa longer than they have been elsewhere. Calculations suggest all modern humans are descended from a population of African H. sapiens numbering as few as 10,000.

2. The Regional Continuity Hypothesis suggests that regional populations of H. erectus evolved into H. sapiens through interbreeding between the various populations. Evidence from the fossil record and genetic studies supports this idea.

Scientists can often use the same “evidence” to support contrasting hypotheses depending on which evidence (fossils or molecular clock/ DNA studies) one gives more weight to. The accuracy of the molecular clock, so key to the out-of-Africa hypothesis, has recently been questioned.

Recent studies on the Y-chromosome seem to weaken the regional continuity hypothesis by indicating a single point-of-origin for our species some 270,000 years ago. Continued study will no doubt reveal new evidence and undoubtedly new hypotheses will arise. It is a task for all of us to weigh the evidence critically and reach a supportable conclusion, whether we are scientists or not.

Essay # 3. H istory of the Primates:

Before Homo:

The evolutionary history of the primates can be traced back for some 85 million years, as one of the oldest of all surviving placental mammal groups. Most paleontologists consider that primates share a common ancestor with the bats, another extremely ancient lineage, and that this ancestor probably lived during the late Cretaceous, together with the last dinosaurs. The oldest known primates come from North America, but they were widespread in Eurasia and Africa as well, during the tropical conditions of the Paleocene and Eocene.

With the beginning of modern climates, marked by the formation of the first Antarctic ice in the early Oligocene around 40 million years ago, primates went extinct everywhere but Africa and southern Asia. One such primate from this time was Notharctus.

Fossil evidence found in Germany 20 years ago was determined to be about 16.5 million years old, some 1.5 million years older than similar species from East Africa. It suggests that the primate lineage of the great apes first appeared in Eurasia and not Africa.

The discoveries suggest that the early ancestors of the hominids (the family of great apes and humans) migrated to Eurasia from Africa about 17 million years ago, just before these two continents were cut off from each other by an expansion of the Mediterranean Sea. These primates flourished in Eurasia and that their lineage leading to the African apes and humans —Dryopithecus—migrated south from Europe or Western Asia into Africa.

The surviving tropical population, which is seen most completely in the upper Eocene and lowermost Oligocene fossil beds of the Fayum depression southwest of Cairo, gave rise to all living primates—lemurs of Madagascar, lorises of Southeast Asia, galagos or “bush babies” of Africa, and the anthropoids; platyrrhines or New World monkeys, and catarrhines or Old World monkeys and the great apes and humans.

The earliest known catarrhine is Kamoyapithecus from uppermost Oligocene at Eragaleit in the northern Kenya rift valley, dated to 24 mya (millions of years before present). Its ancestry is generally thought to be close to such genera as Aegyptopithecus, Propliopithecus, and Parapithecus from the Fayum, at around 35 mya.

There are no fossils from the intervening 11 million years. No near ancestor to South American platyrrhines, whose fossil record begins at around 30 mya, can be identified among the North African fossil species, and possibly lies in other forms that lived in West Africa that were caught up in the still-mysterious transatlantic sweepstakes that sent primates, rodents, boa constrictors, and cichlid fishes from Africa to South America sometime in the Oligocene.

In the early Miocene, after 22 mya, many kinds of arboreally adapted primitive catarrhines from East Africa suggest a long history of prior diversification. Because the fossils at 20 mya include fragments attributed to Victoriapithecus, the earliest cercopithecoid, the other forms are (by default) grouped as hominoids, without clear evidence as to which are closest to living apes and humans.

Among the presently recognised genera in this group, which ranges up to 13 mya, we find Proconsul, Rangwapithecus, Dendropithecus, Limnopithecus, Nacholapithecus, Equatorius, Nyanzapithecus, Afropithecus, Heliopithecus, and Kenyapithecus, all from East Africa.

The presence of other generalised non-cercopithecids of middle Miocene age from sites far distant—Otavipithecus from cave deposits in Namibia, and Pierolapithecus and Dryopithecus from France, Spain and Austria—is evidence of a wide diversity of forms across Africa and the Mediterranean basin during the relatively warm and equable climatic regimes of the early and middle Miocene.

The youngest of the Miocene hominoids, Oreopithecus, is from 9 mya coal beds in Italy.

Molecular evidence indicates that the lineage of gibbons (family Hylobatidae) became distinct between 18 and 12 Ma, and that of orangutans (subfamily Ponginae) at about 12 Ma; we have no fossils that clearly document the ancestry of gibbons, which may have originated in a so far unknown South East Asian hominid population, but fossil proto-orangutans may be represented by Ramapithecus from India and Griphopithecus from Turkey, dated to around 10 Ma.

It has been suggested that species close to last common ancestors of gorillas, chimpanzees and humans may be represented by Nakalipithecus fossils found in Kenya and Ouranopithecus found in Greece.

Molecular evidence suggests that between 8 and 4 mya, first the gorillas, and then the chimpanzee (genus Pan) split off from the line leading to the humans; human DNA is 98.4 percent identical to the DNA of chimpanzees. We have no fossil record, however, of either group of African great apes, possibly because bones do not fossilize in rain forest environments.

Hominines, however, seem to have been one of the mammal groups (as well as antelopes, hyenas, dogs, pigs, elephants, and horses) that adapted to the open grasslands as soon as this biome appeared, due to increasingly seasonal climates, about 8 mya, and their fossils are relatively well known.

The earliest are Sahelanthropus tchadensis (7- 6 mya) and Orrorin tugenensis (6 mya), followed by:

1. Ardipithecus (5.5-4.4 mya), with species Ar. kadabba and Ar. Ramidus.

2. Australopithecus (4-2 mya), with species Au. anamensis, Au. afarensis, Au. africanus, Au. bahrelghazali, and Au. Garhi.

3. Kenyanthropus (3-2.7 mya), with species Kenyanthropus platyops.

4. Paranthropus (3-1.2 mya), with species P. aethiopicus, P. boisei, and P. robustus.

5. Homo (2 mya-present), with species Homo habilis, Homo rudolfensis, Homo ergaster, Homo georgicus, Homo antecessor, Homo cepranensis, Homo erectus, Homo heidelbergensis, Homo rhodesiensis, Homo sapiens neanderthalensis, Homo sapiens idaltu, Archaic Homo sapiens, Homo floresiensis.

Essay # 4. Genus of Homo:

The word homo is Latin for “human”, chosen originally by Carolus Linnaeus in his classification system. It is often translated as “man”, although this can lead to confusion, given that the English word “man” can be generic like homo, but can also specifically refer to males. Latin for “man” in the gender-specific sense is vir (pronounced weer), cognate with “virile” and “werewolf”. The word “human” is from humanus, the adjectival form of homo.

In modern taxonomy, Homo sapiens are the only extant species of its genus, Homo. Likewise, the ongoing study of the origins of Homo sapiens often demonstrates that there were other Homo species, all of which are now extinct. While some of these other species might have been ancestors of H. sapiens, many were likely our “cousins”, having speciated away from our ancestral line.

There is not yet a consensus as to which of these groups should count as separate species and which as subspecies of another species. In some cases this is due to the paucity of fossils, in other cases it is due to the slight differences used to classify species in the Homo genus. The Sahara pump theory provides an explanation of the early variation in the genus Homo.

i. Homo Habilis:

H. habilis lived from about 2.4 to 1.4 million years ago (mya). H. habilis, the first species of the genus Homo, evolved in South and East Africa in the late Pliocene or early Pleistocene, 2.5-2 mya, when it diverged from the Australopithecines.

H. habilis had smaller molars and larger brains than the Australopithecines, and made tools from stone and perhaps animal bones. One of the first known hominids, it was nicknamed ‘handy man’ by its discoverer, Louis Leakey. Some scientists have proposed moving this species out of Homo and into Australopithecus.

ii. Homo Rudolfensis and Homo Georgicus:

These are proposed species names for fossils from about 1.9 -1.6 mya, the relation of which with H. habilis is not yet clear. H. rudolfensis refers to a single, incomplete skull from Kenya. Scientists have suggested that this was just another habilis, but this has not been confirmed.

H. georgicus, from Georgia, may be an intermediate form between H. habilis and H. erectus, or a sub-species of H. erectus.

iii. Homo Ergaster and Homo Erectus:

The first fossils of Homo erectus were discovered by Dutch physician Eugene Dubois in 1891 on the Indonesian island of Java. He originally gave the material the name Pithecanthropus erectus based on its morphology that he considered to be intermediate between that of humans and apes.

H. erectus lived from about 1.8 mya to 70,000 years ago. Often the early phase, from 1.8 to 1.25 mya, is considered to be a separate species, H. ergaster, or it is seen as a subspecies of erectus, Homo erectus ergaster.

In the Early Pleistocene, 1.5-1 mya, in Africa, Asia, and Europe, presumably, Homo habilis evolved larger brains and made more elaborate stone tools; these differences and others are sufficient for anthropologists to classify them as a new species, H. erectus. In addition H. erectus was the first human ancestor to walk truly upright.

This was made possible by the evolution of locking knees and a different location of the foramen magnum (the hole in the skull where the spine enters). They may have used fire to cook their meat.

A famous example of Homo erectus is Peking Man; others were found in Asia (notably in Indonesia), Africa, and Europe. Many paleoanthropologists are now using the term Homo ergaster for the non-Asian forms of this group, and reserving H. erectus only for those fossils found in the Asian region and meeting certain skeletal and dental requirements which differ slightly from ergaster.

iv. Homo Cepranensis and Homo Antecessor:

These are proposed as species that may be intermediate between H. erectus and H. heidelbergensis.

H. cepranensis refers to a single skull cap from Italy, estimated to be about 800,000 years old.

H. antecessor is known from fossils from Spain and England that are 800,000-500,000 years old.

v. Homo Heidelbergensis:

H. heidelbergensis (Heidelberg Man) lived from about 800,000 to about 300,000 years ago. Also proposed as Homo sapiens heidelbergensis or Homo sapiens paleohungaricus.

vi. Homo Neanderthalensis:

H. neanderthalensis lived from about 250,000 to as recent as 30,000 years ago. Also proposed as Homo sapiens neanderthalensis- there is ongoing debate over whether the ‘Neanderthal Man’ was a separate species, Homo neanderthalensis, or a subspecies of H. sapiens.

While the debate remains unsettled, evidence from mitochondrial DNA and Y-chromosomal DNA sequencing indicates that little or no gene flow occurred between H. neanderthalensis and H. sapiens, and, therefore, the two were separate species.

vii. Homo Rhodesiensis, and the Gawis Cranium:

H. rhodesiensis, estimated to be 300,000-125,000 years old, most current experts believe Rhodesian Man to be within the group of Homo heidelbergensis though other designations such as Archaic Homo sapiens and Homo sapiens rhodesiensis have also been proposed.

In February 2006 a fossil, the Gawis cranium, was found which might possibly be a species intermediate between H. erectus and H. sapiens or one of many evolutionary dead ends. The skull from Gawis, Ethiopia, is believed to be 500,000-250,000 years old.

Only summary details are known, and no peer reviewed studies have been released by the finding team. Gawis man’s facial features suggest its being either an intermediate species or an example of a “Bodo man” female.

viii. Homo Sapiens:

H. sapiens (“sapiens” means wise or intelligent) has lived from about 250,000 years ago to the present. Between 400,000 years ago and the second interglacial period in the Middle Pleistocene, around 250,000 years ago, the trend in cranial expansion and the elaboration of stone tool technologies developed, providing evidence for a transition from H. erectus to H. sapiens.

The direct evidence suggests that there was a migration of H. erectus out of Africa, then a further speciation of H. sapiens from H. erectus in Africa (there is little evidence that this speciation occurred elsewhere). Then a subsequent migration within and out of Africa eventually replaced the earlier dispersed H. erectus.

This migration and origin theory is usually referred to as the single- origin theory. However, the current evidence does not preclude multiregional speciation, either. This is a hotly debated area in paleoanthropology.

Current research has established that human beings are genetically highly homogenous, that is the DNA of individuals is more alike than usual for most species, which may have resulted from their relatively recent evolution or the Toba catastrophe. Distinctive genetic characteristics have arisen, however, primarily as the result of small groups of people moving into new environmental circumstances.

These adapted traits are a very small component of the Homo sapiens genome and include such outward “racial” characteristics as skin color and nose form in addition to internal characteristics such as the ability to breathe more efficiently in high altitudes.

H. sapiens idaltu, from Ethiopia, lived from about 160,000 years ago (proposed subspecies). It is the oldest known anatomically modern human.

ix. Homo Floresiensis :

H. floresiensis, which lived about 100,000-12,000 years ago has been nicknamed hobbit for its small size, possibly a result of insular dwarfism. H. floresiensis is intriguing both for its size and its age, being a concrete example of a recent species of the genus Homo that exhibits derived traits not shared with modern humans.

In other words, H. floresiensis share a common ancestor with modern humans, but split from the modern human lineage and followed a distinct evolutionary path. The main find was a skeleton believed to be a woman of about 30 years of age. Found in 2003 it has been dated to approximately 18,000 years old. Her brain size was only 380 cm 3 (which can be considered small even for a chimpanzee). She was only 1 meter in height.

However, there is an ongoing debate over whether H. floresiensis is indeed a separate species. Some scientists presently believe that H. floresiensis was a modern H. sapiens suffering from pathological dwarfism.

Use of Tools:

Using tools has been interpreted as a sign of intelligence, and it has been theorized that tool use may have stimulated certain aspects of human evolution—most notably the continued expansion of the human brain. Paleontology has yet to explain the expansion of this organ over millions of years despite being extremely demanding in terms of energy consumption.

The brain of a modern human consumes about 20 Watts (400 kilocalories per day), which is one fifth of the energy consumption of a human body. Increased tool use would allow for hunting and consuming meat, which is more energy-rich than plants. Researchers have suggested that early hominids were thus under evolutionary pressure to increase their capacity to create and use tools.

Precisely when early humans started to use tools is difficult to determine, because the more primitive these tools are (for example, sharp-edged stones) the more difficult it is to decide whether they are natural objects or human artifacts.

Stone Tools:

Stone tools are first attested around 2.6 million years ago, when H. habilis in Eastern Africa used so-called pebble tools, choppers made out of round pebbles that had been split by simple strikes.

This marks the beginning of the Paleolithic, or Old Stone Age; its end is taken to be the end of the last Ice Age, around 10,000 years ago. The Paleolithic is subdivided into the Lower Paleolithic (Early Stone Age, ending around 350,000-300,000 years ago), the Middle Paleolithic (Middle Stone Age, until 50,000-30,000 years ago), and the Upper Paleolithic.

The period from 700,000-300,000 years ago is also known as the Acheulean, when H. ergaster (or erectus) made large stone hand-axes out of flint and quartzite, at first quite rough (Early Acheulian), later “retouched” by additional, more subtle strikes at the sides of the flakes.

After 350,000 BP (Before Present) the more refined so-called Levallois technique was developed. It consisted of a series of consecutive strikes, by which scrapers, slicers (“racloirs”), needles, and flattened needles were made. Finally, after about 50,000 BP, ever more refined and specialised flint tools were made by the Neanderthals and the immigrant Cro-Magnons (knives, blades, skimmers). In this period they also started to make tools out of bone.

Essay # 5. Evolution of Neanderthals :

Archaic H. sapiens lived from 500,000 to 30,000 years ago and combined features of H. sapiens with those of H. erectus. The Neanderthals, considered in this group, lived in Europe and western Asia between 100,000 and 30,000 years ago before their disappearance.

Neanderthals were larger-brained than modern humans, had a sloping forehead, prominent brow ridges and a receding chin. They had a very prominent nose and ranged in height from 5 foot 2 inches (average female) to 5 foot 6 inches (average male).

Despite their image as brutish simpletons, Neanderthals were the first humans to bury their dead with artifacts, indicating abstract thought, perhaps a belief in an after-life. They lived in free-standing settlements, as well as caves. Neanderthal tools were more sophisticated than H. erectus’ tools, employing handles to gain extra leverage.

Did Neanderthals evolve gradually into modern humans, or were they replaced by modern forms originating from a single population? The answer to that depends on the answer to the question of the origin of H. sapiens from H. erectus. The out-of-Africa hypothesis suggests Neanderthals were a separate species (H. neandertalensis) replaced as modern humans (H. sapiens) spread from Africa. The regional continuity hypothesis suggests Neanderthals were a subspecies (H. sapiens neandertalensis) that evolved into modern humans (H. sapiens sapiens).

Agriculture and Migrations :

Since the evolution of H. erectus, migrations have been a fact of human existence, helping to spread genetic diversity as well as technological innovation. The most recent innovations have not been physical, but rather cultural.

The Neolithic transition, about 10,000 years ago, involved the change from hunter-gatherer societies to agricultural ones based on cultivation of plants and domesticated animals. Evidence suggests this began in the Middle East and spread outward via migrations. Genetic studies suggest agriculture spread by the migration of farmers into hunter-gatherer societies. This would produce a genetic blurring as the farmers interbred with the indigenous peoples, a pattern supported by genetics.

Most anthropologists agree that the New World was populated by a series of three migrations over the temporary land connection between Asia and North America. The Immigrants spread southward, eventually reaching Tierra del Fuego in the southernmost part of South America.

Anthropological and linguistic studies find three groups of peoples:

1. The Amerinds, who spread across North and South America.

2. The Na-Denes, who occupied the northwestern region of North America.

3. The Eskaleuts, Eskimo and Aleut peoples who live in the far north.

Mitochondrial DNA studies find four distinct groups descended from peoples of Siberia. Amerind mtDNA suggests two waves of migration (one perhaps as old as 21-42 thousand years ago). The genetic model confirms the accepted ideas about human migration into the Americas and suggests a possible fourth wave.

Essay # 6. Models of Human Evolution:

Today, all humans are classified as belonging to the species Homo sapiens sapiens. However, this is not the first species of hominids- the first species of genus Homo, Homo habilis evolved in East Africa at least 2 million years ago, and members of this species populated different parts of Africa in a relatively short time.

Homo erectus evolved more than 1.8 million years ago, and by 1.5 million years ago had spread throughout the Old World. Virtually all physical anthropologists agree that Homo sapiens evolved out of Homo erectus.

Anthropologists have been divided as to whether Homo sapiens evolved as one interconnected species from H. erectus (called the Multiregional Model, or the Regional Continuity Model), or evolved only in East Africa, and then migrated out of Africa and replaced H. erectus populations throughout the Old World (called the Out of Africa Model or the Complete Replacement Model).

Anthropologists continue to debate both possibilities, and the evidence is technically ambiguous as to which model is correct, although most anthropologists currently favor the Out of Africa model.

Multiregional Model :

Advocates of the Multiregional model, primarily Milford Wolpoff and his followers, have argued that the simultaneous evolution of H. sapiens in different parts of Europe and Asia would have been possible if there was a degree of gene flow between archaic populations.

Similarities of morphological features between archaic European and Chinese populations and modern H. sapiens from the same regions, Wolpoff argues, support a regional continuity only possible within the Multiregional model. Wolpoff and others further argue that this model is consistent with clonal patterns of phenotypic variation.

Out of Africa Model :

According to the Out of Africa Model, developed by Christopher Stringer and Peter Andrews, modern H. sapiens evolved in Africa 200,000 years ago. Homo sapiens began migrating from Africa between 70,000 – 50,000 years ago and would eventually replace existing hominid species in Europe and Asia.

The Out of Africa Model has gained support by recent research using mitochondrial DNA (mtDNA). After analysing genealogy trees constructed using 133 types of mtDNA, they concluded that all were descended from a woman from Africa, dubbed Mitochondrial Eve.

A variation on this model involves the Southern dispersal theory, which has gained support in recent years from genetic, linguistic and archaeological evidence. In this theory, there was a coastal dispersal of modern humans from the Horn of Africa around 70,000 years ago. This group helped to populate Southeast Asia and Oceania, explaining the discovery of early human sites in these areas much earlier than those in the Levant.

A second wave of humans dispersed across the Sinai peninsula into Asia, resulting in the bulk of human population for Eurasia. This second group possessed a more sophisticated tool technology and was less dependent on coastal food sources than the original group. Much of the evidence for the first group’s expansion would have been destroyed by the rising sea levels at the end of the Holocene era.

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• v.371(1698); 2016 Jul 5

The origin and evolution of Homo sapiens

If we restrict the use of Homo sapiens in the fossil record to specimens which share a significant number of derived features in the skeleton with extant H. sapiens , the origin of our species would be placed in the African late middle Pleistocene, based on fossils such as Omo Kibish 1, Herto 1 and 2, and the Levantine material from Skhul and Qafzeh. However, genetic data suggest that we and our sister species Homo neanderthalensis shared a last common ancestor in the middle Pleistocene approximately 400–700 ka, which is at least 200 000 years earlier than the species origin indicated from the fossils already mentioned. Thus, it is likely that the African fossil record will document early members of the sapiens lineage showing only some of the derived features of late members of the lineage. On that basis, I argue that human fossils such as those from Jebel Irhoud, Florisbad, Eliye Springs and Omo Kibish 2 do represent early members of the species, but variation across the African later middle Pleistocene/early Middle Stone Age fossils shows that there was not a simple linear progression towards later sapiens morphology, and there was chronological overlap between different ‘archaic’ and ‘modern’ morphs. Even in the late Pleistocene within and outside Africa, we find H. sapiens specimens which are clearly outside the range of Holocene members of the species, showing the complexity of recent human evolution. The impact on species recognition of late Pleistocene gene flow between the lineages of modern humans, Neanderthals and Denisovans is also discussed, and finally, I reconsider the nature of the middle Pleistocene ancestor of these lineages, based on recent morphological and genetic data.

This article is part of the themed issue ‘Major transitions in human evolution’.

1. Introduction: the big questions in modern human origins

The first question which should be addressed in any discussion of the origin and evolution of Homo sapiens is which diagnosis of the species is going to be used. A paper using the classic multiregional concept of H. sapiens [ 1 , 2 ] would probably need to cover the whole Pleistocene history of the human genus, while the much more restricted usage of authors such as Tattersall & Schwartz [ 3 ] might require a focus limited to a small set of middle–late Pleistocene fossils. In this paper, I will use the term H. sapiens for material that appears morphologically more closely related to extant humans than to the clade of Homo neanderthalensis , one of two potentially closest fossil relatives of extant H. sapiens (the other being Denisovans, which are so far virtually unknown from fossil material) [ 4 ]. Furthermore, although other researchers, particularly archaeologists, include behavioural factors in their diagnoses of modern humans/ H. sapiens , I will not do so here.

Extant H. sapiens share specific traits such as a high neurocranium, rounded in lateral profile, a small face retracted under the frontal bone, a true chin even in infants, small discontinuous supraorbital tori, a lengthened post-natal growth period and life history, and a narrow trunk and pelvis with short superior pubic rami. Anatomical characterization of the H. sapiens lineage should thus be possible from features such as cranial globularity, retrocessive face, basicranial flexion, development of a mental osseum, dental microstructure and pelvic shape [ 5 – 8 ]. In addition, distinctive morphologies of elements of inner ear anatomy are being increasingly well characterized in H. sapiens [ 9 ]. In the cranial vault, the shape of the parietal region in H. sapiens seems particularly distinctive [ 10 – 12 ] and makes a significant contribution to globularity in both lateral and occipital views. Basicranial flexion is a more complex feature, but H. sapiens certainly appears distinctive in various measurements of this [ 6 , 13 ]. Dental microstructure, especially with the advent of micro-CT and synchrotron technology, is not only demonstrating the extended ontogeny of H. sapiens , but also revealing clear differences between H. sapiens and other hominin species in features such as enamel thickness and the shape of the enamel–dentine junction [ 14 ].

A second major question concerns the mode of evolution of the species H. sapiens —whether this was relatively punctuational or gradual. As the African middle Pleistocene hominin record is still sparse and poorly dated, it is not yet possible to tell whether fossils such as Omo Kibish 1 and Herto 1 and 2 represent some of the earliest coalescences of most of the traits we associate with our extant species, or whether more ancient examples remain to be found or dated. In Europe, the recent redating of the Sima de los Huesos fossils to at least 400 ka suggests that many Neanderthal features, particularly in the face, jaws and teeth, were already well developed by that time [ 15 , 16 ], which is more than double the age estimate for Omo Kibish 1 (McDougall) [ 17 ]. The subsequent European record had indicated a gradual, though not always precisely ordered, accretion of further Neanderthal synapomorphies [ 18 ], though a better absolute chronology is needed to test this properly. So at our present state of knowledge, we cannot yet say if there was an asymmetry between Europe (early) and Africa (late) in the appearance of the most diagnostic traits of the respective Neanderthal and modern human clades (and see further discussion at the end of this paragraph). Weaver [ 19 ] discussed three bodies of evidence often used to support a punctuational origin for H. sapiens in Africa (the apparent distinctiveness of ‘archaic’ from ‘modern’ fossil morphologies in Africa; the coalescence of extant mtDNAs to approx. 200 ka in Africa; the date of the first African appearance of ‘modern’ morphology apparently lying close to that date). He critiqued this evidence and used population and quantitative genetics theory to show that lengthy process models are also consistent with these data, and provide a viable alternative for modern human origins. A related consideration is whether differences along the respective neanderthalensis and sapiens lineages arose randomly, as a result of drift, or under the action of selection. Using cranial measurements, Weaver et al . [ 20 ] demonstrated that the level of difference between the two species could have arisen under drift rather than selection over a timescale of approximately 400 kyr, with the additional possibility that this divergence was relatively unconstrained due to cultural buffering, compared with the morphological divergence shown between crania of subspecies of Pan troglodytes [ 21 ]. And finally, when considering the rate of evolution of Neanderthal and modern human traits, Trinkaus [ 22 ] found that there was asymmetry in the amount of change along the two lineages, with the modern one being more derived than the Neanderthal one. However, limited genetic data seem to suggest the opposite, i.e. the Neanderthal lineage might be the more derived [ 23 ].

A third question is the nature of the last common ancestor (LCA) of the sapiens and neanderthalensis lineages, and when that LCA lived. Since 1983, I have built the case that shape resemblances between the Broken Hill and Petralona crania indicate the existence of a widespread middle Pleistocene population which can be called Homo heidelbergensis if the Mauer mandible is also included, or H. rhodesiensis if it is not [ 24 , 25 ] (see also [ 26 ]). Moreover, I have argued that this species represents the most reasonable LCA for the neanderthalensis and sapiens lineages, with their common origin placed at about 400 ka based on the estimated mtDNA coalescence date of the two lineages [ 25 , 27 ]. A new study using geometric morphometrics of various crania to virtually reconstruct the LCA of Neanderthals and modern humans also found that an Afro-European species ( H. heidelbergensis s.l. ) most closely approached the hypothetically reconstructed LCA, with the added suggestion that the LCA most likely lived in Africa [ 28 ]. An alternative model has a much older proposed LCA for the neanderthalensis and sapiens lineages, based on the ‘modern’ maxillary conformation of the ATD6-69 H. antecessor face from Gran Dolina, Atapuerca, dated approximately 850 ka [ 29 ]. Such a model would imply that this facial morphology was retained in the descendant sapiens lineage, but was lost in that of the Neanderthals. New data are emerging that are relevant to these models concerning the ultimate ancestry of H. sapiens and H. neanderthalensis (and thus also of the Denisovans), and I will return to this issue in §5.

A fourth question follows from the previous ones. Once the Neanderthal and modern human lineages began to evolve, did more ancient (and perhaps ‘ancestral’) morphologies in Eurasia and Africa soon die away, or could they have persisted alongside their ‘descendants’ for a considerable time? And if the latter, might the contemporaneous lineages have exchanged genes? While such a question poses serious issues for any simple cladistic, phylogenetic or taxonomic schemes, there is growing evidence of the survival of what could be considered as earlier middle Pleistocene morphologies (cf. H. heidelbergensis or H. rhodesiensis ) into at least the later middle Pleistocene of Europe and Africa [ 8 , 25 ]. In addition, recent evidence of late Pleistocene episodes of introgression between different human lineages in Eurasia [ 30 ] and perhaps also in Africa [ 31 ] shows us that comparable genetic exchanges could also have been occurring in the middle Pleistocene.

2. The African middle–early late Pleistocene fossil record of Homo sapiens

The fossil record available to reconstruct the evolution of H. sapiens in Africa is still relatively sparse and poorly dated, and is dominated by material from the fossiliferous sedimentary basins of East Africa. Huge expanses of Central and West Africa were clearly inhabited during the later middle Pleistocene, as shown by the evidence of artefacts, but not a single informative fossil has yet been recovered to identify who those early inhabitants were. Thus, the available record is probably highly biased and unrepresentative of the continent as a whole. Nevertheless, we have to work with what is available, and I will now briefly discuss the most complete or significant specimens discovered so far, region by region ( figure 1 ). Wider and more detailed compilations on the material and its dating can be found in Schwartz & Tattersall [ 32 ], Millard [ 33 ], Klein [ 34 ] and Wood [ 35 ].

Left lateral views of African and Israeli archaic and early modern Homo sapiens crania (replicas unless otherwise stated). Top (L to R): Florisbad, Jebel Irhoud 1, Jebel Irhoud 2 (original), Eliye Springs, Guomde (reversed), Omo 2. Bottom (L to R): Omo 1, Herto (original, reversed), Ngaloba, Singa, Skhul 5, Qafzeh 9.

(a) North-west and North Africa

In Morocco, the later middle Pleistocene archaeological record probably changes from non-Aterian Middle Palaeolithic/Middle Stone Age (MSA) industries to those of the Aterian during Marine Isotope Stage (MIS) 6, although it seems likely that a non-Aterian MSA continues in some regions alongside and even after the Aterian [ 36 , 37 ].

The Jebel Irhoud cave was exposed during quarrying operations in a Baryte mine and since 1961 has produced faunal remains, non-Aterian MSA archaeology and at least seven fossil hominins, with several more specimens found since 2007 awaiting publication. The fossil human remains are from low in the stratigraphic sequence, the best known being a cranium (JI1), a calvaria (JI2) and the mandible of a child (JI3) [ 38 ]. The cranium is relatively long and low with smooth rather than angular contours. It has a strong continuous supraorbital torus anterior to a somewhat domed frontal, and parallel-sided cranial vault with a capacity of about 1305 cm 3 [ 39 ]. The face is large and especially broad in its upper dimensions, with flat angled cheekbones and a broad but low nose, below which is significant alveolar prognathism. JI2 is a somewhat larger, more robust and angular calvaria, with a cranial capacity of approximately 1400 cm 3 [ 39 ]. It has a greater occipital projection and angulation, more modern parietal and frontal shape, but equally strong supraorbital development. Although comparisons of midline contours suggest H. sapiens affinities for both cranial vaults, multivariate studies indicate somewhat closer affinities for JI2 to recent human samples [ 40 , 41 ]. Both display some phenetic resemblances to early modern specimens such as those from Qafzeh, Skhul and Herto, though they lack their upper parietal expansion. In cranial vault (but not facial) form, there is nevertheless an overall resemblance to the Sima fossils and other early Neanderthals. The JI3 immature mandible presents a rather contrasting gracile body and large posterior teeth, and anteriorly may show incipient chin development. JI4 is a robust partial humerus, despite its immaturity, while there is also a further immature pelvic fragment. Overall, there is enough preserved of JI1 to indicate that it does not represent anatomically modern H. sapiens , although there are hints of ‘modern’ basicranial flexion in the relationship of the face and vault. JI2 and 3 are more difficult to assess because of their incompleteness, but the teeth of Irhoud 3 were subjected to synchrotron analysis which suggested an age at death of about 8 years, and a modern developmental pattern [ 42 ]. At the same time, an ESR analysis of its tooth enamel suggested an age of approximately 160 ka, which seems very likely to be a minimum figure.

The Rabat ( Kebibat ) hominin from Morocco consists of a very fragmentary cranial vault with more complete upper and lower jaws. The large teeth are typical of middle Pleistocene specimens from North Africa, but the mandible has elements of a mental trigone and a vertical symphysis, while the occipital region is high and relatively rounded [ 38 ]. However, the individual is subadult and so caution must be exercised in interpreting its morphology. Faunal correlation places the Rabat specimen in the late middle Pleistocene.

The Moroccan cave of Dar-es-Soltan II has produced an immature calvaria, an adolescent mandible and the anterior part of a skull with associated hemimandible. The anterior vault of DeS5 is high and very large, with a strong but divided supraorbital torus over a low, broad and flat face, with a low but broad nose. There are indications of a canine fossa and of alveolar prognathism. The mandible and the preserved posterior dentition are also large, but illustrations are deceptive in indicating the lack of a chin—the symphysial region is in fact broken off. Deciding on how to classify DeS5 is difficult—it has a rather modern-looking face and frontal bone shape, but both are very large in size, as is the supraorbital development. Although previous assessments have suggested that it could represent an Aterian intermediate between the MSA-associated Irhoud specimens and those of the Iberomaurusian (i.e. local late Upper Palaeolithic), morphometric analyses place it closer to Jebel Irhoud 1 and the Qafzeh crania than to the late Pleistocene fossils [ 36 ].

The caves of El-Aliya and Témara (Morocco) have produced fragmentary human cranial fossils from MSA/Aterian contexts. The Aliya material includes a large maxilla and teeth, but despite previous assertions, the preserved cheek morphology seems rather flat and non-Neanderthal [ 43 ]. However, not enough is preserved for definitive statements about the affinities of the material. The Témara specimens consist of some vault fragments, lacking a supraorbital torus and a mandible, which can more definitely be allied with modern H. sapiens .

A number of other Aterian sites have produced dental material which was analysed by Hublin et al . [ 43 ]. The cave of Zouhrah at El Harhoura yielded a mandible and canine during excavations in 1977, while the Grotte des Contrabandiers (Temara) has been under intermittent excavation since 1955 with early discoveries of material such as a robust and large-toothed mandible (in 2009 a still-unpublished immature human skeleton was recovered from Aterian levels apparently dated to MIS5). The Aterian dental samples generally display very large dimensions compared with late Pleistocene H. sapiens and Neanderthals. However, a relatively smaller anterior dentition and thicker enamel on the molars are more modern traits. While crown morphologies are generally complex, they resemble material like Skhul and Qafzeh more closely in pattern than the Neanderthals.

In contrast to the large and complex molar morphology found in the Moroccan Aterian material, the only teeth in the posterior mandible fragments recovered from ‘levalloiso-mousterian’ deposits in the Libyan cave of Haua Fteah in the 1950s are small and simple-crowned. The mandible fragments both have rather low rami and no evidence of retromolar spaces. As far as can be judged from the limited morphology preserved, these appear to represent H. sapiens , with an age now estimated at approximately 70 ka, within the early part of MIS4 [ 44 ]. Another possibly MSA-associated specimen which lacks the dental size and complexity of the Moroccan Aterian material is the cranium and fragmentary skeleton of a child recovered within sand deposits on the top of Taramsa Hill , Egypt [ 45 ]. Enough of the cranial vault is preserved to indicate a modern shape, even before cleaning, but the postcranial skeleton was highly friable and little of it survives. The MSA age of the specimen could not be definitively confirmed by direct dating [ 46 ].

(b) Southern Africa

The Florisbad ‘cranium’ (in fact only the anterior part of a skull and face) was found at this open locality in South Africa in 1932, stratified in a long sequence which remained poorly dated until 1996, when ESR on an enamel fragment from the human fossil provided an age estimate of approximately 259 ka [ 47 ]. The frontal bone is wide, thick and relatively receding, and the supraorbital torus is high but not strongly projecting, with lateral reduction. The face is incomplete but is certainly very broad in its upper proportions, with some expression of a canine fossa. In R. Clarke's reconstruction, it is low relative to its great breadth, but allowing for a complete anterior dentition, as in P. Cohen's unpublished reconstruction ( figure 1 ), it may well have been closer to the Broken Hill cranium in facial height. Florisbad has sometimes been seen as morphologically allied to Broken Hill, at other times as an early member of the H. sapiens clade, and at yet other times as possibly representing a distinct late Middle Pleistocene species H. helmei , either a precursor species to H. sapiens [ 48 ], or as the LCA of the Neanderthal and modern clades, and the originating species of Mode 3 (levallois) lithic technology [ 49 ]. While too incomplete for definitive assignment, like the Irhoud material this fossil probably represents an archaic part of the H. sapiens clade.

The Klasies River Mouth fossil human material has been recovered over a period of more than 40 years in a variety of MSA-related stratigraphic contexts from an interrelated complex of caves on the southern coast of South Africa [ 34 ]. The material is fragmentary and represents mandibular, maxillary, facial, cranial vault and postcranial elements. The mandibles display great variation, ranging from large and chinless through ones with an apparently modern symphysial morphology, to a very small, albeit robust corpus with tiny teeth. Two maxillary fossils show comparable variation in size, while an isolated zygomatic is robust but of modern aspect, despite claims to the contrary. An apparently adult frontal fragment displays a wide interorbital breadth but centrally has a modern supraorbital profile. The few recovered postcranial bones indicate small-bodied individuals, although a proximal ulna has relatively large joint surfaces. Some elements of the Klasies assemblages clearly conform to the modern H. sapiens pattern, but other material cannot be so readily assigned on the parts preserved.

Border Cave , South Africa, has produced a number of fossil or subfossil human remains of actual or possible MSA antiquity [ 50 ]. In the 1940s, a humerus, ulna fragment and two metatarsals were recovered out of context in a spoil heap but have been argued on preservation grounds to be of MSA age. Their size and robusticity suggest that they might represent the same individual as the Border Cave 1 partial skull also found in spoil. This ‘skull’ actually consists of only part of the upper face and vault, but enough is preserved to show its large size, domed frontal, small supraorbital development and wide interorbital breadth. Although it appears of modern aspect, its large size and frontal and upper facial shape discriminate it from recent populations, and the possibly associated humerus and ulna display a few archaic traits. An edentulous mandible (BC2) recovered around the same time is small and more lightly built and appears assignable to anatomically modern H. sapiens on size and symphysial morphology. The infant skeleton BC3 certainly appears to represent H. sapiens , and has an important association with perforated Conus shells and red pigment [ 51 ]. Like BC2, the BC5 partial mandible is small and has a modern symphysial morphology, and its importance has been enhanced by direct ESR dating, providing an age estimate of approximately 74 ka [ 50 ].

(c) East Africa

The Eliye Springs (ES-11693) cranium was discovered by tourists after rapid changes in lake levels at West Turkana, Kenya [ 52 ]. The cranium had suffered anterior erosion, particularly of the face, but enough is preserved to reveal an archaic morphology. The vault is long and inferiorly broad, with limited upper parietal expansion, parallel-sided in rear view. There is slight frontal keeling but cranial buttressing is not strongly expressed, although it is not possible to assess the full extent of supraorbital torus development due to erosion, which has exposed the frontal sinuses. The occipital contour is rather rounded with minimal development of an occipital torus. Although heavily eroded, the face appears to resemble some late middle Pleistocene African crania in being relatively short, flat and broad, and there are signs of the slight development of a canine fossa. Although ES-11693 was discovered with faunal remains, the lack of any secure context or associated archaeology means that it remains undated. What is preserved of the specimen does not suggest particular H. sapiens affinities, although there are regional characteristics in facial shape and vault form that may relate it to other middle Pleistocene African crania such as Florisbad, Jebel Irhoud 1, Singa and Ngaloba. However, like Singa (see below, this section) its shape may have been affected by pathology [ 53 ].

Seven fragmentary cranial and mandibular fossils have been recovered from sediments bordering Lake Eyasi in Tanzania since the 1930s. Possible association with Acheulian artefacts had suggested an earlier rather than later middle Pleistocene age, but limited ESR and U-series age estimates from fauna associated with frontal 7 suggest an age approximately between 88 and 130 ka. Eyasi 1 has a projecting but not massive supraorbital torus on its frontal, while its occipital is more modern in torus formation compared with a much stronger development in Eyasi 2, even displaying a possible suprainiac fossa. Frontal 7, like Eyasi 1, shows a rather low frontal bone with a distinct but not massive torus. The fragmentary condition of the material and difficulties of reconstruction limit the information available beyond indications that these specimens are apparently not assignable to anatomically modern H. sapiens [ 54 , 55 ], despite the later Pleistocene date suggested for some of them.

Ngaloba Laetoli Hominid 18 was recovered from the Ngaloba beds in the Laetoli region of Tanzania [ 56 ]. This partial cranium may date from the late middle or early late Pleistocene [ 57 ]. It is relatively long and low with an elongated and receding frontal bone. It is rather rounded posteriorly in both rear and lateral views, with negligible development of an occipital torus, but anteriorly there is a prominent but thin supraorbital torus. The occipitomastoid region is interesting for its resemblance to that of Neanderthals in the relation of mastoid and juxtamastoid eminences. The face cannot be properly articulated with the vault, but it is evidently rather low, broad and flat in the midface, with canine fossae, giving way to a prognathic subnasal region. The reconstruction by Cohen [ 58 ] confirms the relative gracility of the face, but suggests a greater height than in other depictions. Workers such as Rightmire [ 59 ] have classified LH18 as fundamentally modern, but it does not conform to anatomically modern H. sapiens in overall morphology, despite a suggestive facial and parietal shape.

Three Omo Kibish fossil hominins were discovered in 1967 in separate localities and contexts. Omo 1 was a partial skeleton in Member I of the Kibish Formation, Omo 2 an isolated surface find of a calvaria and Omo 3 a frontal fragment from member III [ 60 ]. More recently, an American-led expedition has located the original sites of Omo 2 and Omo 1, recovering more human material, including further parts of Omo 1, and additional fossils [ 61 , 62 ]. The fragmented skull from the Omo 1 assemblage has been the subject of several reconstructions but all concur in indicating a high, rounded and voluminous cranial vault with an occipital morphology of sapiens configuration, albeit with a wide frontal bone and strong but partitioned brow ridges. The face, dentition and mandible are much more fragmentary but evidence a canine fossa and mental eminence [ 63 ]. The postcranial remains include fragmentary limb bones which are largely of modern aspect, although with some distinctive features also noted in Neanderthal, Skhul-Qafzeh and Upper Palaeolithic individuals [ 61 ], and with proportions comparable with those of recent East Africans [ 64 ]. Omo 2 also has a very large braincase, with an endocranial capacity of approximately 1435 cm 3 , but is narrower, with parallel-sided rather than superiorly expanded parietals, and a strongly angled occipital bone bearing a high but not especially projecting occipital torus. It also displays parasagittal flattening either side of a midline keel. In contrast with these archaic features, the supraorbital torus is a weakly expressed prominence at the anterior end of a flat, broad and receding frontal bone. The ages of Omo 1 and 2 have been sources of much controversy, but now seem well established at approximately 195 ka [ 17 , 65 ]. Classifying the Omo material is difficult. It is evident that Omo 1 can be assigned to modern H. sapiens from the preserved parts, but Omo 2 can only be tentatively placed in the clade through the apomorphy of supraorbital reduction.

The two separate human fossils found in the Guomde Formation of East Turkana in 1971 and 1976 consist of a proximal femur fragment KNM-ER 999 and a partial skull KNM-ER 3884 [ 66 ]. The femur is strongly built but seemingly of modern aspect in shaft shape and cross section [ 67 ] while the partial skull seems to combine characteristics found in Omo Kibish 1 and 2. It is similarly large and high, with a rounded modern-looking occipital region like Omo 1, but looking much more like Omo 2 in rear profile, high, with vertical walls. The supraorbital torus, as reconstructed, is evenly thick and projecting. Direct uranium-series dating of the material suggests an age of more than 180 ka [ 68 ].

Several cranial and dental human fossils were recovered from an open site at Herto in Ethiopia in 1997 [ 69 ]. The most significant consist of a nearly complete adult skull, an immature calvaria and parts of another cranial vault, probably adult. All are very large in size, the adult skull having a capacity of approximately 1450 cm 3 . The length of the skull is outside the range of over 5000 modern crania, but its high and relatively globular shape (except for the occipital) conforms to the H. sapiens pattern. The supraorbital torus is strong and projecting, although divided into lateral and central parts, but the angled occipital with its centrally strong torus is reminiscent of that of Broken Hill 1 and Jebel Irhoud 2. The rear of the separate cranial fragments indicates an even greater size and robusticity than the most complete cranium. Univariate and multivariate analyses showed that the combination of features of the adult skull differentiate it from recent humans, but in terms of cranial shape, cranial angles and neurocranial globularity, it can be classified as H. sapiens , perhaps of comparable grade to material from Qafzeh & Skhul [ 70 ]. Its modernity was reaffirmed in metrical studies by Lubsen & Corruccini [ 71 ] and McCarthy & Lucas [ 72 ]. However, the addition of the subspecific nomen idaltu [ 69 ] does not seem justified.

The Singa calvaria was discovered in a block of calcrete in the seasonally dry bed of the Blue Nile in Sudan in 1924. It was notable for its strong parietal bosses, which were argued by some workers to link it to Khoisan origins, despite its great distance from southern Africa [ 73 ]. It has a well marked but centrally divided supraorbital torus, flat upper face and wide interorbital spacing, while the frontal is quite high. However, the parietals are very short and the occipital is also short and protruding, without showing a transverse torus. Natural breakage allowed removal of calcrete filling the endocranium, revealing the parietal bosses were abnormally thickened by diploic bone. An endocranial mould indicated a cranial capacity of about 1400 cm 3 , while its asymmetry suggested a left-handed individual [ 74 ]. CT-scanning revealed further evidence of pathology in the unilateral absence of the inner ear on the right side, and Spoor et al . [ 75 ] suggested labyrinthine ossification had occurred, following an infection of the labyrinth membrane. This may have been due to a blood-borne infection (such as septicaemia) or a blood disorder such as anaemia, which fits with some explanations for the parietal pathology. Because of its pathology, it is unclear how abnormal is the shape of the calvaria. Overall, the anterior cranial morphology looks fairly modern, but the parietals are abnormal, preventing proper taxonomic assessment. The fossil is dated to a minimum age of 131–135 ka by U-series dating on sediments from the inside of the calvaria, and ESR analyses on associated faunal remains [ 76 ].

(d) Western Asia (Skhul and Qafzeh)

Although not in Africa, the adjacent Levant has clearly been a conduit for ancient population movement between Africa and Eurasia. Material such as the Zuttiyeh fronto-facial fragment, probably from the middle Pleistocene, remains difficult to classify, but in my view it does not show clear Neanderthal or modern human affinities, as can also be argued for the approximately 400 ka dental sample from Qesem [ 77 ]. Later and more clearly diagnosable material usually assigned to MIS5 also comes from Israel, in the form of the Tabun 1 Neanderthal skeleton, and the material I will discuss in more detail from the caves of Skhul and Qafzeh.

The site of Mugharet es-Skhul comprises a small cave, and a larger external rock-shelter and terrace, with most of the archaeological and hominin remains coming from the latter. The Skhul fossils, comprising 10 individuals, were discovered by Ted McCown in 1931–1932 as part of a larger rescue dig in the Mount Carmel area directed by Dorothy Garrod [ 78 ]. There is evidence that at least some of the Skhul individuals were intentionally buried [ 79 ], which may explain their relatively good preservation. Skhul 4 and 5 have significant portions of cranial and postcranial material preserved, while Skhul 9 consists of a more fragmentary calvaria and face with fragments of the pelvis and a femur. At one stage, Skhul was believed to be only around 40 ka in age, based on faunal and lithic similarities to Tabun, the Middle Palaeolithic levels of which had supposedly been dated to about 40 ka using radiocarbon. However, the Skhul material (Skhul 2, 5 and 9) has now been dated to between approximately 100 and 130 ka using ESR, U-series and luminescence analyses [ 80 ]. Nevertheless, it remains possible that Skhul 9 is older than the other fossils, as suggested by its morphology and lower stratigraphic position [ 48 , 80 ].

The first discoveries from Qafzeh Cave and its terrace (including Qafzeh 6) were made in the 1930s, but the full study and publication of the Qafzeh specimens only really began in the 1970s, by which time new excavations were greatly enlarging the Middle Palaeolithic-associated sample to 16 individuals. Vandermeersch's monographic work on the still-growing series [ 81 ] demonstrated that the Skhul and Qafzeh samples shared Middle Palaeolithic associations, the apparent presence of symbolic burials, and significant skeletal similarities. In terms of morphology, Vandermeersch highlighted the H. sapiens ( sensu stricto ) affinities of both groups of hominins from their cranial and mandibular shape to their pelves and limb bones. Non-metric, metric and morphometric analyses have regularly supported the view that the cranial, dental and postcranial anatomy of the combined Skhul-Qafzeh sample represents an early form of H. sapiens sensu stricto , albeit with robust or primitive features (e.g. [ 82 – 88 ]). As with Skhul, the application of luminescence, ESR and U-series dating has also placed the Middle Palaeolithic material into MIS5, with age estimates ranging approximately from 90 to 120 ka [ 89 ].

While the Skhul and Qafzeh series show clear derived traits in cranial and postcranial anatomy shared with Upper Palaeolithic and recent humans, they also display considerable variation, and differ in aspects of cranial shape and morphology, both within and between the samples (e.g. [ 3 , 48 ]). Given the wide error ranges on the available physical dating of the sites and skeletal and archaeological material [ 57 ], it is currently impossible to determine whether the Skhul and Qafzeh specimens represent different samples from essentially the same variable MIS5 population, as is often assumed in palaeoanthropological studies, two distinct populations, perhaps separated by many millennia, or even a sample of hominins covering a long period of time at both sites.

3. Interpreting the African middle–late Pleistocene fossil human record

During the past 25 years, the Recent African Origin model has increasingly dominated discussions about the evolution of H. sapiens , but with the recent modifications to it demanded by evidence of introgression from archaic humans such as Neanderthals and Denisovans outside Africa [ 90 ]. The date of origin of H. sapiens in this model has also changed in the face of new discoveries and dating work and is now often placed at about 200 ka, with the generally accepted first appearance of ‘anatomically modern humans’ (that is to say fossils that predominantly share the skeletal morphology of extant humans) in the form of the Omo Kibish 1 skeleton and the somewhat younger Herto material. This usage is consistent with my previous only partly successful attempts at diagnosing H. sapiens through a ‘working definition’ delimited by recent skeletal, and particularly, cranial variation in traits such as a domed neurocranium, reduction in facial size and projection, and increased basicranial flexion [ 63 , 91 , 92 ].

If it is accepted that H. sapiens is a relatively young species, distinct from Neanderthals and from the putative LCA, H. heidelbergensis , there are a number of possible schemes for the evolution of H. sapiens , three of which are illustrated in figure 2 . One possibility would be to limit the species diagnoses of both H. neanderthalensis and H. sapiens to those samples which predominantly share the morphological traits of the terminal members of the Neanderthal and modern human clades, e.g. post-MIS8 Neanderthals, and post-MIS8 H. sapiens . Primitive members of the Neanderthal and sapiens clades that showed only some of the diagnostic features of the terminal species could then be given a separate species name. If this scheme were to be followed, the species ‘intermediate’ between H. heidelbergensis and H. sapiens would probably by priority be H. helmei , based on the Florisbad partial cranium [ 48 ]—note that this is a distinct usage of the species name from that of Foley & Lahr, [ 49 ]. The equivalent nomen for specimens ‘intermediate’ between H. heidelbergensis and H. neanderthalensis would probably then be H. steinheimensis by priority ( figure 2 a ). Yet as explained in Stringer & Buck [ 4 ], unless there is truly punctuational change at each species origination, there would undoubtedly be blurred and probably unworkable boundaries between helmei and sapiens , and between s teinheimensis and neanderthalensis . Given that there are already difficulties in distinguishing the LCA from the early stages of evolution along the respective sapiens and neanderthalensis lineages, creating further taxonomic divisions for such relatively short-lived populations would merely atomize the taxonomic problems rather than solve them.

( a ) H. sapiens and H. neanderthalensis as species represented only as terminal taxa, with all the traits judged to be diagnostic. H. helmei and H. steinheimensis as intermediate species between each terminal species and LCA, here suggested to be H. heidelbergensis . ( b ) Looser diagnoses of H. sapiens and H. neanderthalensis including all populations after the split from the LCA. Both species encompass considerable morphological variation along their lineages and populations which go extinct without issue. The overall topography of both trees and the estimated divergence and LCA ‘dates’ are derived from a study of whole mtDNA genomic data [ 25 , 27 ]. ( c ) A tree which uses the new date and Neanderthal-like morphology of the Sima sample, plus an inferred deeper divergence date based on new genomic mutation rate estimates [ 93 ]. Here, a hypothetical and older ‘Ancestor X’ replaces heidelbergensis as the LCA. The Denisovans are also shown on the diagram, as an early derivative of the Neanderthal clade. Their taxonomic status is still unclear [ 30 ]. Late Pleistocene inter-lineage gene flow is indicated by the dashed arrows [ 30 , 94 , 95 ]. (Online version in colour.)

Another option would be to employ looser definitions of H. sapiens and H. neanderthalensis to encompass all the samples which lie on the respective lineages after their separation from the LCA ( figure 2 b ). The early members of the modern human lineage could be informally termed ‘archaic H. sapiens ’, and the early members of the Neanderthal lineage ‘early H. neanderthalensis ’ which, although it lacks taxonomic precision, is my present preference. Unfortunately, the term ‘archaic H. sapiens ’ has previously been used much more loosely, often referring to specimens as different as Broken Hill and La Chapelle-aux-Saints, but I think its use could be restricted to specimens with a predominance of archaic features but which nevertheless demonstrably belong to the phylogenetic clade of extant H. sapiens . One day we may be able to map more fossils onto their respective lineages through their aDNA, as has now proved possible for the Sima specimens, placed within the Neanderthal clade via genomic DNA [ 93 ]. However, this method would be entirely dependent on aDNA preservation, and is likely to prove impractical for much of the material recovered from warmer depositional environments. The early parts of both the H. sapiens and H. neanderthalensis lineages are also likely to show some of the lost diversity that once existed and will thus contain populations which might ultimately not be ancestral to late members of either species, as shown notionally in figure 2 —but see further discussion in §4.

4. Early Homo sapiens in Africa

Figure 1 illustrates the wide morphological variation in fossil human crania associated (or potentially associated) with early MSA archaeology in Africa, ranging from material like Florisbad and Jebel Irhoud through to Ngaloba and Herto. The figure also includes examples from Skhul and Qafzeh. This array of fossils shows differing combinations of archaic and derived (recent H. sapiens -like) traits, and illustrates some of the variation displayed even at closely related sites.

As discussed, Omo Kibish 1 and 2 contrast strongly in cranial shape. A transition between their morphologies would provide a different model of H. sapiens evolution from that suggested by Herto, and this is perhaps exemplified in the ER-3884 partial cranium from Guomde which shows features found in both the Kibish crania. These potential variations already suggest that there is probably not a simple, linear relationship between an ancestral heidelbergensis -like morphology and that of H. sapiens . Alternatively, as suggested by Stringer [ 2 , 8 , 70 ], this variation might instead reflect the coexistence of morphologically distinct populations during the later middle Pleistocene in Africa. Evolution may at times have progressed independently in different areas, with morphological substructure leading on to the eventual coalescence of the full suite of H. sapiens characteristics, comparable with the pattern seen in the genetic data. I have called this an ‘African multiregionalism’, with many potentially interfertile subdivisions of the evolving sapiens species across Africa [ 2 , 8 , 70 ]. Others (e.g. [ 96 ]) have used the analogy of a braided stream for what they consider to be an open genetic network for different human lineages across the whole Old World, but I think the most appropriate application for this analogy is in the middle Pleistocene of Africa. The imperfect chronological control over the African middle Pleistocene record provides only very limited support for an ordered progression from ‘archaic sapiens ’ to ‘modern sapiens ’ through time. Instead we see morphologically varied fossils such as Broken Hill, Florisbad and Omo Kibish 1 apparently juxtaposed in close temporal proximity [ 8 ]. There is also growing evidence of the survival of even younger elements of archaic morphology into the late Pleistocene at sites like Eyasi, Iwo Eleru and Lukenya Hill (e.g. [ 40 , 41 , 97 – 99 ]).

While later Pleistocene Eurasia suffered both large-scale and sharp millennial-scale climatic oscillations, which were especially reflected in fluctuations of temperature, these changes in Africa were expressed much more in terms of precipitation (e.g. [ 100 , 101 ]). This would have led to the creation or removal of biogeographic barriers such as tropical rainforests and deserts—both probably largely impenetrable to early humans [ 8 , 100 , 102 ]. In turn, this could have had direct demographic effects on human populations. For example, the middle of MIS6 (approx. 150 ka) was predominantly arid, with the probable isolation or even extinction of small human populations across Africa. By contrast, the warmest part of MIS5 (approx. 120 ka) may have been a time of population expansions and interconnections. However, this may not always have led to homogenization, as Scerri et al . note for the ‘green’ Sahara [ 37 ], where distinct palaeobiomes may have catalysed enduring subdivisions. Refugia in which populations could weather the worst of climatic downturns have been suggested as a key driver of morphological and perhaps adaptive behavioural changes in Eurasia [ 8 , 103 ], but in Africa climatic ameliorations could have been equally important in seeding denser and more networked populations, facilitating both genetic and cultural changes [ 8 , 101 , 104 ]. The result of these processes was the composite we call modern H. sapiens , genetically, morphologically and behaviourally, but there was never a single centre of origin, and despite later homogenization [ 82 ], some ancient substructure could have persisted.

Several relatively late Pleistocene African sites contain fossils that exhibit combinations of archaic and recent H. sapiens traits. In my doctoral research, I found that, despite its Late Stone Age associations and overall ‘modern’ shape, the Iwo Eleru fossil from Nigeria was idiosyncratic, since it also showed affinities to archaic fossils such as Ngandong, Saccopastore 1 and Omo 2 [ 10 , 11 ]. Its dating was recently confirmed as late Pleistocene (approx. 14 ka) but also confirmed was its morphological distinctiveness from recent African crania. Despite its late date, it showed morphometric shape affinities to the much older Elandsfontein, Ngaloba, and Skhul and Qafzeh fossils [ 40 , 41 ]. A comparable though slightly earlier example of late Pleistocene distinctiveness (approx. 22 ka) is the Lukenya Hill partial calvaria from Kenya, which was restudied by Tryon et al . [ 98 ], showing a similar mix of more archaic and recent elements of cranial shape. These specimens emphasize how little we still know about late Pleistocene morphological variation across much of the African continent. These fossils may indicate deep Pleistocene population substructural variation, possibly including hybridization between late H. sapiens and surviving archaic hominin lineages [ 8 , 30 , 40 , 92 ], variation which was subsequently lost.

5. Discussion

Based on this research, there are genetic traces in extant H. sapiens of earlier introgression from at least three extinct human groups [ 30 , 92 , 94 , 95 ]. So how does this affect any definition of H. sapiens in the fossil record? As Jolly [ 105 , p. 129] stated in comparing the taxonomy of recent papionins and of fossil hominins ‘The message … is to concentrate on biology, avoid semantic traps and realize that any species-level taxonomy based on fossil material is going to be only an approximate reflection of real-world complexities’. As long as the biological species concept (which does not operate well for many closely related extant species of birds and mammals) is not imposed, species can be recognized in the fossil record as evolutionary lineages which maintain their identity through significant periods of time (and in the face of small amounts of introgression). On that basis, I consider that both H. neanderthalensis and H. sapiens can be treated as species with a time depth that stretches back into the middle Pleistocene. However, that pragmatic use of the term ’species’ must be tempered with a recognition that these ‘species’ were not genetically impermeable.

As this paper includes the origin of H. sapiens in its title, it seems appropriate to return to this topic, with relevant new data to add to the picture. For some time, it has been recognized that the immature ATD6-69 face which forms part of the hypodigm of H. antecessor displays apparent resemblances to extant H. sapiens in the confirmation of the zygomaxillary area. For example, its anterior surface is angled at about 90° to the midline, its inferior border is retracted and runs approximately horizontally, with a malar notch and zygomaxillary tubercle, and there is a canine fossa in the infraorbital area. For some, this morphology in a fossil dated at more than 800 ka may reflect the ancestral condition for H. sapiens [ 29 ]. Previously [ 2 ], I questioned whether this morphology would have been maintained in the adult, and whether there would have been population variation in its expression, but it does seem to be expressed in three more fragmentary subadult and adult specimens from Gran Dolina [ 106 ]. Issues have also been raised about allometric effects on the zygomaxillary area such that larger archaic faces would show an inflated maxillary morphology more like that of the massive Bodo and Petralona crania [ 107 ]. Friedline et al . [ 108 ] conducted a wide-ranging morphometric study of the faces of various fossil crania in order to better place ATD6-69 developmentally and phylogenetically. They confirmed that its morphology was largely shared with H. sapiens and that this would probably have persisted into adulthood. However, they argued that this morphology was largely primitive and that it had probably evolved and re-evolved several times in human evolution, and therefore had to be used with caution phylogenetically. In their view, the true ‘modern’ zygomaxillary morphology could only be reliably traced back to later middle Pleistocene fossils such as Jebel Irhoud 1.

But there are further relevant data. First, microscopic study of the facial growth of the immature ATD6-69 antecessor fossil confirmed that it does show homologies with the maxillary developmental pattern of recent H. sapiens , a pattern argued to be derived, not primitive [ 109 ], while a second study has concluded that the facial ontogeny of immature Sima de los Huesos fossils (dated approx. 400 ka) instead show homologies with later neanderthalensis specimens [ 110 ]. Thus, deriving the Sima and Neanderthal facial morphologies from that of the Gran Dolina child would demand evolutionary reversals in their ontogeny, while deriving H. sapiens from it would apparently not. And it has been recognized for some time (e.g. [ 32 ]) that if we examine the African middle Pleistocene record we find the majority of fossils with the area preserved share much of the zygomaxillary morphology of most extant H. sapiens in having an anterior surface angled at about 90° to the midline, an approximately horizontal lower border, and a flat or retracted infraorbital surface in lateral view (which may include a canine fossa). However, African fossils that I assign to H. heidelbergensis / rhodesiensis are divided into ones which although damaged or incomplete, apparently display a more sapiens -like zygomaxillary morphology (Thomas Quarry and Ndutu), and those that do not (Bodo, Broken Hill). If this is not a reflection of sexual dimorphism or allometric factors at work in the large faces of Bodo 1 and Broken Hill 1 (as I have sometimes argued), it may indicate taxonomic diversity in the African middle Pleistocene record which could exclude those fossils from representing an ancestral morph for H. sapiens .

New genetic data add further complexity to reconstructing the nature and dating of the LCA of Neanderthals and modern humans. As already mentioned, mtDNA indicates that the LCA lived approximately 400 ka, consistent with a heidelbergensis origin [ 27 ]. However, as also discussed, the clear Neanderthal morphological and genetic affinities of the Sima fossils, now dated to at least 400 ka, suggest there was probably an evolutionary divergence well before that date. Moreover, using the latest estimates of the autosomal human mutation rate, the divergence date of the neanderthalensis and sapiens lineages can indeed be placed earlier, between 550 and 765 ka, which would be consistent with only the oldest suggested examples of heidelbergensis as potentially representing the LCA [ 93 ]. An alternative would be to consider a H. antecessor -like morphology as more likely for the LCA of H. sapiens and H. heidelbergensis, with the heidelbergensis group exemplified by Arago, Petralona, Bodo and Broken Hill having more in common facially with the Sima fossils and subsequent Neanderthals ( figure 2 c ).

It has been suggested that the antecessor material also displays a derived sapiens -like pattern of dental development [ 111 ], as well as some similarities in postcranial morphology [ 106 ], but in other respects there are Neanderthal-like features such as in the mastoid region, hypertrophied medial pterygoid tubercle, M 1 shape, clavicle and humerus. Bermúdez de Castro & Martinón-Torres [ 106 ] concluded that antecessor was a side-branch of a lower Pleistocene radiation of lineages in Eurasia that eventually gave rise to Neanderthals in Europe and to H. sapiens in Africa. If heidelbergensis ( sensu Stringer [ 25 ]) is not the LCA for sapiens and neanderthalensis because of a derived facial morphology and because the known fossils post-date the actual divergence date, then what did the LCA look like (Ancestor X in figure 2 c ). It may have displayed a morphology of the lower face more like antecessor than heidelbergensis , but what about the rest of the cranium and the dentition? Mounier et al . [ 112 ] argued that, despite its younger age, the Ceprano calvaria displays the most primitive morphology of the heidelbergensis group. Unfortunately, it lacks the crucial facial region, but perhaps its cranial form is a retention of the shape that typified the LCA in the early middle Pleistocene. In considering dental morphology, we are severely limited by the lack of good data for this period from sub-Saharan Africa, while further north the Tighennif fossils from Algeria have been considered more primitive than the antecessor material [ 113 ]. However, endostructurally, the Tighennif dentitions were considered close to the status of a Neanderthal-modern LCA by Zanolli & Mazurier [ 114 ].

There are perhaps also clues in the form of the Qesem teeth from Israel, which are of comparable age to or slightly younger than the Sima de los Huesos fossils (approx. 400 ka). According to Hershkovitz et al . [ 77 ], these teeth combine features found in the Neanderthals with some typical of the early modern Skhul and Qafzeh samples. Given the much earlier presence of Neanderthal-like traits in the antecessor and Tighennif materials, we should consider the possibility that the LCA did display some Neanderthal-like features dentally. In the past, I have tended to envisage the LCA as ideally totally plesiomorphous, and thus lacking the derived features of either Neanderthals or modern humans. But in reality, the LCA may in fact have shown a mosaic of primitive and derived traits, with the latter differentially inherited in the descendant lineages. Thus, the cranial vault may have been Ceprano-like, the facial morphology antecessor -like and retained in the sapiens line in Africa, while the dentition may have been more Neanderthal-like than previously envisaged, and then increasingly modified in the modern human lineage. New studies and discoveries should allow the proper testing of these ideas in the next few years.

Acknowledgements

I wish to thank the Royal Society (especially Jenna Lane) and my co-organizers of Major Transitions in Human Evolution (Rob Foley, Marta Lahr and Lawrence Martin) for an excellent conference. This paper benefitted greatly from contributions made to that conference and to those at ESHE 2015, as well as from the constructive comments of two reviewers. I wish to thank Ali Freyne for all her help with the text and figures, the Photographic Unit of the NHM, Tim White and Günter Bräuer for supplying material for figure 1 .

Competing interests

I declare I have no competing interests.

I thank the Calleva Foundation and the Human Origins Research Fund of the NHM for supporting my research.

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Human evolution: short essay on human evolution.

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Man is a product of evolution. Therefore human evolution is intimately related to the origin of life and its development on the face of earth. It is customary to speak of evolution ‘from amoeba to Man’, as if the amoeba is the simplest form of life. But in reality, there are several organisms more primitives than amoeba, say for example viruses. The evolution from a self-replicating organic molecule to a protozoan, like amoeba, is the most complex step in evolution, which might have consumed the same extent of time from protozoan to man.

The term evolution was first applied by the English philosopher Herbert Spencer to mean the historical development of life. Since then evolution denotes a change, although the term may be defined in several ways. In the context of man, the biological evolution started with the ‘Origin of life’. In the beginning, there was nothing. The first successful formation of protoplasm initiated the life and its continuous development proceeded towards complexity to give rise different life forms of evolved type.

About 10 billion years after the formation of Universe, the earth was formed. Life on earth appeared far late, nearly three billion years ago. Of the several evolutionary problems, perhaps the origin of life is the most critical, since there is no record concerning it. Life has been characterized by the capacity of performing certain vital functional activities like metabolism, growth and reproduction. There is no ambiguity regarding this point. But how the first life came on earth is a matter of conjecture.

Ancient thinkers speculated that life originated spontaneously from inorganic components of the environment, just after the formation of earth. A series of physio-chemical processes were perhaps responsible behind this creation. Aristotle (384 BC to 322 BC) was the pioneer in this line of thought and nobody raised any voice against his speculation till seventeenth Century. But in seventeenth Century, an Italian scientist, Francesco Redi (1627 -1697) made an experiment with two pieces of meat.

One of the pieces was kept fully covered and the other piece was kept in an open place. After some days he examined both of the pieces very carefully. He noticed that, flies laid eggs on the uncovered piece of meat and so many new flies had born. But the covered piece of meat had not produced any new fly, as there was absolutely no access of flies.

Redi tried to establish the fact, that living organisms cannot be originated spontaneously from inorganic components. More or less at the same time, Leuwenhock (1632 – 1723) by studying several microorganisms like protozoa, sperm, bacteria etc. under microscope declared that the spontaneous generation was possible for the microorganisms. Later, Louis Pasteur (1822 -1895) also studied much to furnish evidences in support of spontaneous creation.

In fact, scientists of this period were perplexed in finding out how life began spontaneously as a matter of chance. Philosophers, Thinkers and Scientists all had submitted their varied thought and propositions regarding the nature and mechanism of origin of life on earth. Different religions had also put forth different concepts in this connection.

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Essay on Human Evolution

Students are often asked to write an essay on Human Evolution in their schools and colleges. And if you’re also looking for the same, we have created 100-word, 250-word, and 500-word essays on the topic.

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100 Words Essay on Human Evolution

Introduction.

Human evolution is the lengthy process of change by which people originated from apelike ancestors. It’s a fascinating journey that took millions of years.

The Beginning

Our story begins in Africa about 6 million years ago. The first humans were primates, similar to apes.

Walking Upright

Around 4 million years ago, early humans started walking upright. This trait, called bipedalism, set us apart from other apes.

Use of Tools

About 2.6 million years ago, humans started using tools. This was a major step in our evolution.

Development of Language

Human evolution is a fascinating subject. It helps us understand where we come from and who we are.

250 Words Essay on Human Evolution

Introduction to human evolution.

Human evolution is an intriguing scientific concept that traces the progression of Homo sapiens from our early ancestors. It is a multidimensional process that has been shaped by natural selection, genetic drift, migration, and mutation over millions of years.

The Early Beginnings

The journey of human evolution began approximately 6 million years ago in Africa, with the emergence of the first hominins, our earliest ancestors. These hominins were distinguished from apes by their upright posture and bipedal locomotion.

The Genus Homo

Around 2 million years ago, the genus Homo appeared, characterized by a significant increase in brain size and the advent of tool use. Homo habilis, Homo erectus, and eventually Homo sapiens, our species, were part of this genus. Homo sapiens are unique in their capacity for complex language, abstract thought, and creativity.

The Role of Environment

Environmental changes played a critical role in human evolution. For instance, climate fluctuations led to the development of traits like bipedalism, which allowed early hominins to adapt to diverse habitats.

Modern Humans and Migration

The story of human evolution is a testament to our species’ adaptability and resilience. It underscores the dynamic interplay between biology and environment, shaping our past and influencing our future. As we continue to unravel the mysteries of our evolution, we gain profound insights into what it means to be human.

500 Words Essay on Human Evolution

Human evolution is a fascinating and complex process that has shaped us into the beings we are today. It is a multidisciplinary field of science that encompasses biology, anthropology, archaeology, and genetics. The process of evolution involves a series of natural changes that cause species to arise, adapt to the environment, and eventually become extinct.

The Origins of Homo Sapiens

Over time, evolutionary pressures such as environmental changes and competition for resources led to the emergence of new hominin species. Around two million years ago, the genus Homo, which includes modern humans, emerged. The Homo species had larger brains and made sophisticated tools.

The Advent of Homo Sapiens

Approximately 300,000 years ago, Homo sapiens, our own species, appeared. Early Homo sapiens had a combination of physical traits from earlier hominin species and new traits that we still possess today, such as a high forehead and a chin. They also exhibited advanced behaviors, such as creating complex tools and engaging in symbolic behavior like art and burial rituals.

Migration and Modern Evolution

The Homo sapiens began to migrate out of Africa around 70,000 years ago, gradually populating the entire globe. They adapted to a variety of environments and developed diverse cultures. This migration and adaptation are reflected in the genetic diversity we see in modern humans.

Modern human evolution continues today. Humans are still evolving, with natural selection acting on traits such as resistance to diseases and the ability to digest certain foods. Furthermore, our cultural and technological advancements are now a significant driver of our evolution.

The journey of human evolution is a testament to the resilience and adaptability of our species. It is a complex process that has shaped our physical traits, behaviors, and cultures. As we continue to evolve and adapt to our changing world, we carry with us the legacy of millions of years of evolution. Understanding our evolutionary history not only helps us appreciate our place in the natural world but also sheds light on our future as a species.

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Hominids and Stages of Human Evolution Essay

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Evolution theory explains the change in the human species’ characteristics over generations based on archeological evidence. The cultural behaviors of early hominids are altered with the changes in physical features. Ardipithecus ramidus, Australopithecines, Homo habilis, Homo erectus, and Homo Neanderthal are stages of human evolution with distinct physical appearances and behavior. Earlier, man’s biological and cultural characteristics evolved gradually in response to different environmental factors.

Ardipithecus ramidus is the initial genus of Hominidae that possesses ape-like biological and cultural features. Ardipithecus had rigid pelvis and hind and front limbs implying full bipedal characteristics (Bala, 2020). Ardipithecus displayed a small endocrinal brain capacity (300 to 350 cm3) relative to the body size. These primates were most likely omnivores, suggesting they were hunters and gatherers with a generalized diet of plants, fruits, and meat (Haviland et al., 2015). Similar to other early hominids, Ardipithecus lived in groups in the woods, signified by the tree-climbing skills displayed by their strong limbs.

Australopithecines or Australopithecus had close physical and cultural characteristics with Ardipithecus ramidus. Australopithecus had ape-like physical appearance but bipedal features and small cerebrums (Haviland et al., 2015). At the same time, Australopithecines had smaller canine teeth and massive check jaws, suggesting they were omnivores (Anderson & Tornberg, 2019). The pelvis, limbs, jaws, and teeth of Australopithecus closely resemble humans, but their brain capacity is relatively small (430 cubic centimeters). Australopithecus used tools similar to modern apes, such as sticks and twigs that could effortlessly be redesigned.

Homo habilis was a more advanced human genus than the primitive Australopithecus, exhibited by physical and cultural characteristics. According to Galway-Witham (2019), Homo habilis had a relatively high cranial capacity (500 to 800 cubic centimeters). The foot and hand bones were more human-like, with the ability to manipulate objects hence the name “handy man” (Bala, 2020). The molars and premolars of Homo habilis were comparatively smaller than Ardipithecus and Australopithecus . Homo habilis predominantly lived in grassland environments and could make stone tools such as choppers, scrapers, and flakes, often called Oldowan stone tools.

Homo erectus, identified as “upright man,” exhibited close biological and cultural characteristics to humans. Their body size and shape were identical to humans, although their hips were much broader and more muscular. They had shorter arms with longer legs and could stand upright (Anderson & Tornberg, 2019). Homo erectus skull and teeth were smaller than earlier hominids, although omnivores. The upright man mastered the use of fire and stone to make tools such as knives and scrappers (Galway-Witham, 2019). Homo erectus had a larger brain size than Homo habilis (about 950 cubic centimeters) and could use perishable wood materials and grass to make ropes and strings. Homo erectus were active hunters that did not grow crops but could feed on wild fruits.

Homo Neanderthal is the most recent species of evolution that had analogous features with humans. Neanderthals had an extended lower skull with an enormous nose and a protruded facial shape. With large bones, they were stronger and more muscular than modern humans (Galway-Witham, 2019). Neanderthals made complex tools from stones that they used in scavenging plantations and hunting. They had a significantly higher brain volume of 11,000 low temperatures by using fire to cook, warm their bodies, and protect themselves from wild animals. (Haviland et al., 2015). Culturally, Homo Neanderthals buried the dead and knew how to use fire to make advanced stone technology.

Andersson, C., & Törnberg, P. (2019). Toward a macroevolutionary theory of human evolution: The social protocell. Biological Theory , 14 (2), 86-102.

Bala, S. (2020). Human evolution: insignificant ape to an intelligent designer. International Journal of Advanced Research in Biological Sciences , 7 (12), 6-14. Web.

Galway‐Witham, J., Cole, J., & Stringer, C. (2019). Aspects of human physical and behavioral evolution during the last 1 million years . Journal of Quaternary Science , 34 (6), 355-378.

Haviland, W. A., Prins, H. E., & McBride, B. (2015). The essence of anthropology . Cengage Learning.

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Human evolution conclusion.

There is no scientifically accepted research that shows that humans have stopped evolving. Evolution is certainly still occurring and will continue to occur in humans. Humans exhibit differences in reproductive success, which directly leads to evolution. Humans still face challenges to survival as well, and exhibit variation in heritable traits, all characteristics of evolution. Some of the confusion on this topic likely arises because modern humans have not existed for an extensive period of time, evolutionarily speaking. Many of humanities most esteemed innovations have happened in the past decade or century, merely a few generations at most. However, no innovation will change the fact that humans exhibit varying reproductive success and challenges to survival, the components of evolution.

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Human Origins Studies: A Historical Perspective

• Tom Gundling 1  

Evolution: Education and Outreach volume  3 ,  pages 314–321 ( 2010 ) Cite this article

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Research into the deep history of the human species is a relatively young science which can be divided into two broad periods. The first spans the century between the publication of Darwin’s Origin and the end of World War II. This period is characterized by the recovery of the first non-modern human fossils and subsequent attempts at reconstructing family trees as visual representations of the transition from ape to human. The second period, from 1945 to the present, is marked by a dramatic upsurge in the quantity of research, with a concomitant increase in specialization. During this time, emphasis shifted from classification of fossil humans to paleoecology in which hominids were seen as parts of complex evolving ecosystems. This shift is in no small part due to the incorporation of neo-Darwinian synthetic theory. Finally, technological innovation and changes in social context are considered as influences on human origins studies.

Introduction

Considering the grand sweep of history, the realization that human beings gradually evolved from some non-human ancestor represents a very recent insight. Even so, the goal of this one brief essay cannot be to provide an in-depth description and analysis of every significant development within the field of paleoanthropology, but rather to identify broad patterns and highlight a collection of “events” that are most germane in shaping current understanding of our evolutionary origin. These events naturally include the accretion of fossil material, the raw data which is the direct, if mute, testimony of the past. These fossil discoveries are situated among technological breakthroughs, theoretical shifts, and changes in the sociocultural context in which human origins studies were conducted. It is only through such a contextualized historical approach that we can truly grasp our current understanding of human origins. Foibles of the past remind us to be critical in assessing newly produced knowledge, yet simultaneously we can genuinely appreciate the enormous strides that have been made.

In addition to selective coverage, a second caveat is that this review will focus on research by scientists writing in English. Non-modern hominids Footnote 1 are a cosmopolitan bunch, having been discovered throughout Africa, Asia, and Europe, and there is a significant literature in other languages. In an effort to ameliorate both of these shortcomings, numerous secondary references are included in the bibliography, providing more in-depth information on specific topics. For example, some texts approach the history of paleoanthropology by detailing a single time period (Bowler 1986 ), early human species (Walker and Shipman 1996 ), or researcher (Morell 1995 ), and there are quite a few that consider the subject more comprehensively (Leakey and Goodall 1969 ; Reader 1988 ; Lewin 1997 ; Tattersall 2008 ). In addition, there are a handful of encyclopedia format tomes (Jones et al. 1994 ; Spencer 1997 ; Delson et al. 2000 ), textbooks (Conroy 2005 ; Cela-Conde and Ayala 2007 ; Klein 2009 ), and “coffee table” popular volumes (Stringer and Andrews 2005 ; Johanson and Edgar 2006 ) that in part address the history of human origins studies. Moreover, these texts contain abundant references to the primary literature if that level of scrutiny is desired.

In seeking to provide a useful heuristic framework for the purposes of this particular essay, human origins studies can be broken down into two very broad periods. The first is roughly the century between 1850 and 1950 when research, often conducted by individuals with training outside of anthropology, focused on taxonomy and phylogeny. In other words, although scientists were cognizant that climate change (e.g., northern hemisphere glaciations) would have directly impacted the evolution of early humans, they were mainly interested in collecting “missing links,” naming them, and creating family trees. The second period, from 1950 to the present, is characterized by the relatively rapid development of paleoanthropology as it is currently practiced. Here the emphasis is only partly on the hominids themselves, with ecological context being of equal importance.

The Emergence of Human Origins Studies

This review begins with two mid-nineteenth century developments which are often conflated, but were initially distinct. The first is the acceptance of a temporal association of human material culture (stone tools), with extinct Ice Age mammals (Van Riper 1993 ; Sommer 2007 ). This was significant in that it opened up a considerable prehistory for the human species, well beyond estimates derived from literal scriptural interpretation. However, while acknowledging a lengthy antiquity for the human species, there was, at the time, no reason to suspect that the makers of the stone tools were not fully modern humans in a biological sense. The second major development was the publication of Darwin’s On the Origin of Species in 1859 (Darwin 1859 ). Darwin is rightfully credited with being the most influential, although by no means the first individual to broach the subject of descent with modification, or transmutation theory, as he put it (for an overview of pre-evolutionary ideas related to human origins, see Greene 1959 , Bowler 2003 ). Darwin’s central thesis was that all living species shared a common ancestry, with “endless forms most beautiful” having diverged via natural selection, and although he only briefly mentioned his own species the inference was clear. These two events dovetailed into the now quotidian, but then controversial, notion that humans had evolved over a vast expanse of time (Grayson 1983 ).

While Darwin was initially reticent to discuss human evolution in any detail, his colleague Thomas H. Huxley harbored no such reluctance when he published Man’s Place in Nature: Essays in 1863 (Huxley 1900 ). Darwin freely admitted that the veracity of his audacious proposal would have to withstand paleontological scrutiny and that his theory would collapse in the absence of transitional fossil forms. Huxley’s advantage, beyond his more outspoken personality, was that he actually had a fossil human to describe. The first Neandertal recognized by science was discovered in 1856; however, its description only appeared in English three years later, just as Darwin was going to press (Trinkaus and Shipman 1993 ). Huxley provided a detailed description of the eponymous cranium coupled with carefully composed line drawings (Huxley 1900 ). However, while the importance of the Neandertals in providing empirical evidence documenting an ancient and morphologically distinct human form cannot be discounted, these people hardly bridged the gap separating humans and the great apes. Although a few dissenting voices denied the close evolutionary relationship among humans and the “man-like” apes, and consequently an ape phase of human ancestry, most scientists accepted the overwhelming morphological and embryological evidence in support of just such a relationship. This acceptance was in no small part due to Huxley’s meticulous comparison of gorilla and human anatomy in which he concluded that the gorilla and its close relation, the chimpanzee, represented the nearest approach to humanity in nature.

If Neandertals were more or less human, then more distant, primitive “missing links” remained to be discovered. Just such fossils were recovered on the island of Java in the 1890s by Dutch physician Eugene Dubois, who had traveled to Indonesia as part of the army but with the express purpose of finding the remains of primitive humans (Shipman 2001 ). Java Man consisted of a skull cap, a femur, and a few isolated teeth which taken in combination suggested an early human with a much smaller cranial capacity relative to Neandertals or Homo sapiens (roughly 1,000 vs. 1,500 cubic centimeters), although the femur appeared modern. Dubois did not receive the universal accolades and acceptance he coveted, but his fossils bolstered the conventional wisdom at the time that humans first evolved somewhere in Asia.

During the early twentieth century, the early hominid fossil record grew significantly, if not exponentially, and evolution was widely accepted in scientific circles even while large segments of the lay public remained skeptical. Certainly, there were disagreements over whether natural selection was a sufficient evolutionary mechanism in itself (Bowler 1983 ), but the basic premise of biological change through time was affirmed. The recovery of additional Neandertal remains in Europe refuted lingering claims of pathology regarding the original Neander Valley specimen and solidified the interpretation that the latter was representative of a population of archaic humans occupying Ice Age Europe. Some Neandertal remains were interpreted as not only indicating intentional internment but also associated funerary ritual. The European fossil record was extended significantly with the recovery of a robust lower jaw from Mauer, Germany discovered in 1907.

In 1912 in England, heretofore devoid of non-modern hominid remains despite the prominence of several British scholars in human origins studies, the announcement of hominid fossils from Piltdown was warmly received locally, if with some incredulity abroad. Piltdown was significant since it reified the “brain first” hypothesis, in which primitive humans evolved a large brain before other key human traits evolved. Although a favorite of intelligent design creationism advocates, Piltdown is actually a beautiful example of the scientific method at work, whereby new evidence eventually calls into question prior interpretation, and in this case recognition of intentional fraud (Spencer 1990 ). It was, after all, a new relative dating method measuring the fluorine content of fossils that in 1953 exposed the non-contemporaneity of the jaw and skull. In any case, in the first decades of the twentieth century, a fairly simple human family tree was beginning to emerge (see McCown and Kennedy 1972 and especially Delisle 2007 for exceptions). Relatively small-brained Pithecanthropus led to the more capacious Neandertals and Piltdown, who in turn evolved into modern H. sapiens . Yet the truly ape-like human ancestors remained elusive.

Africa as the Cradle of Humanity

In 1921 a skull bearing superficial resemblance to European Neandertals was recovered as part of mining operations at a place called Broken Hill in Northern Rhodesia (now Zambia). Rhodesian Man marks the recovery of the first in a very long line of non-modern hominids from the African continent. A mere four years later, University of Witwatersrand anatomist Raymond Dart, Australian by birth and having been trained in England, published a brief paper describing the fossil skull of a juvenile “ape” discovered in a limestone quarry near Taung, South Africa. Dart identified certain features of the face, the teeth, the cranium, and the brain of Australopithecus africanus that foreshadowed those of H. sapiens and made the startling claim that what was essentially a bipedal ape signaled the beginning of the human lineage separate from the African great apes.

Initially, with only the one individual, and a juvenile at that, Dart found little support. His most ardent advocate, Scottish physician and paleontologist Robert Broom discovered additional fragmentary remains of the australopithecines, as they were then called, in other South African caves in the 1930s, but these were initially insufficient to sway opinion (Dart 1959 ). This was perhaps due to the near-simultaneous discovery of significant hominid remains from Zhoukoutien (Dragon Bone Hill) in China which quickly eclipsed whatever controversy the diminutive skull from Taung elicited, and despite Broom’s ongoing efforts. As was the case with Java Man, the more complete Chinese fossils fulfilled the expectations of many scientists who anticipated that earliest human ancestors evolved to the East. Comparative analysis of the Javanese and Chinese fossils revealed a great deal of similarity, and all of the fossils were ultimately subsumed in the species Homo erectus .

The Neo-Darwinian Synthesis and the New Physical Anthropology

For several disparate reasons, the decades following the end of World War II (WWII) rather quickly led to a science of paleoanthropology that is recognizably modern. One significant factor relevant in the U.S. if not everywhere, was the dramatic upsurge in enrollment at colleges and universities. The G.I. Bill and subsequent effects of Civil Rights legislation that greatly increased access to higher education meant that millions more students went to college and hence the expansion of existing campuses and programs and in some cases the appearance of entirely new colleges and universities Footnote 2 . As a result, greater numbers of faculty were required who could teach courses and supervise research in diverse academic programs, which in turn led to an attendant rise in the numbers of graduate students themselves who went on to secure positions at institutions of higher learning. Consequently, many disciplines experienced significant increases in research activity, including physical anthropology, and it is worth noting that this was the first generation of researchers whose formal training was in physical anthropology, not in some allied field such as anatomy or medicine. The dramatic rise in practitioners not only increased the knowledge base in terms of simple quantity, but specialization within the field also began to emerge.

A second crucial development that transformed human evolutionary studies was theoretical in nature. Changing ideas regarding the process of evolution had been fermenting and roiling in biology circles for several decades before they infiltrated the study of human origins. In essence, a consensus was reached among biologists ( sensu lato ) that Darwinian natural selection acting on variation arising from random mutation was a sufficient mechanism to explain evolutionary change. For anthropologists, although questions of taxonomy and phylogeny remained important, the intellectual fallout of the so-called neo-Darwinian synthesis led to the “New Physical Anthropology” in which early hominid fossils, rather than representative of some platonic archetype, were interpreted as unique members of variable populations. Focusing on evolution as a process effecting change in populations over time, in contrast to the comparatively myopic sorting of the resulting pattern , arguably represents the most significant theoretical shift in thinking about evolution since Darwin.

Given the comparative de-emphasis on iconic types, the bloated alpha taxonomy of the past was reduced to a mere handful of hominid species displaying previously under-appreciated within species variability. This great reduction in hominid names and consequent simplification of hominid family trees has led some modern scholars to lament what they see as a return to the bad old days of teleology and orthogenesis. Yet there can be little doubt that the “splitting” taxonomic philosophy of the past where almost every new specimen received a new species or quite frequently a new genus name was in dire need of revision.

Just as species types came under scrutiny, so did the concept of evolutionary grades which had up to this point made clear distinctions between the categories of ape and human. While this may have provided some welcome taxonomic clarity, it was artificial in that it ignored the evolutionary reality that at some point members of the human lineage were very ape-like. This realization, obvious in retrospect, led to the widespread acceptance of the South African australopithecines as human ancestors, and the important corollary that bipedalism preceded other distinctive human attributes (Gundling 2005 ).

In addition to increased research activity and theoretical shifts, by the early 1960s technological innovations for the first time permitted the creation of a reliable absolute timescale of human evolution. Comparative protein analysis demonstrated that the African apes were most similar genetically to H. sapiens , inferring their recent common ancestry to the exclusion of other apes and monkeys. Molecular clocks based upon mutation rates and calibrated by the fossil record suggested that this common ancestor lived as little as a few million years ago, although recent estimates put this ancestor at seven to five million years ago. Consequently, known early and middle Miocene ape species became suspect as purported human ancestors, since they preceded the split between the hominid and great ape lineages. Most notably this eventually led to the downfall of Ramapithecus , a Miocene ape genus once widely hailed as a very ancient and very primitive hominid Lewin ( 1997 ).

While molecular studies of living species effectively imposed a theoretical maximum on the age of the hominid lineage, the temporal framework of human origins was further clarified with the introduction of the new potassium argon (K-Ar) method of absolute dating. Louis and Mary Leakey had been scouring the fossil-bearing sediments in and around eastern Africa’s Great Rift Valley for decades when Mary discovered the skull of a robust australopithecine at Olduvai Gorge in 1959. Significantly, Zinjanthropus , the genus coined for the new skull, was discovered within sediments near the base of the Pleistocene Epoch. Volcanic minerals from associated strata were dated to approximately 1.75 million years ago using the K–Ar method, nearly double the age estimated from using other more crude means. This greatly expanded time range certainly bolstered claims for the australopithecines as human ancestors rather than extinct collateral cousins to the “true” human lineage, yet to be discovered.

As an aside, Louis Leakey’s interest in understanding the human past was not limited to the collection of fossils. Sherwood Washburn, a main architect of the new physical anthropology, along with Irven DeVore, conducted pioneering studies of savanna baboons, large-bodied, terrestrial, and highly social primates that served as living proxies for modeling early hominid behavioral ecology (Washburn and DeVore 1961 ). Leakey, on the other hand, took a more phylogenetically based approach and hired scholars to conduct research into the behavior of the great apes as a potential new data source informing hypotheses of early hominid behavior. Jane Goodall was the first, studying chimpanzee behavior at Gombe in Tanzania, then came Dianne Fossey who undertook a longitudinal study of mountain gorillas in Rwanda, and finally Birute Galdikas traveled to Indonesia to conduct field studies of the orangutan (see Kinzey 1987 and De Waal 2001 for more recent primate studies that explicitly address questions of human behavioral evolution).

The emergence of paleoanthropology as a truly multidisciplinary endeavor, concerned with a more holistic picture of our evolutionary past, was a logical extension of the post-WWII new physical anthropology which eschewed simple classification and promoted variable populations as the unit of study. Naturally, these hominid populations did not exist in a vacuum but were components of complex, evolving ecosystems. Hence, field work began to emphasize the collection of greater contextual data in an effort to reconstruct biological and physical environments in which these human ancestors existed and evolved. One of the first field projects to adopt this new approach was an international expedition centered around the Omo River Valley in southern Ethiopia, beginning in 1967. Remarkably, of the 50 papers collected in the resulting volume, only five primarily focus on the hominid remains themselves (Coppens et al. 1976 ).

Early Human Diet and Subsistence

One major aspect of early hominid ecology that occupied researchers engaged in such multidisciplinary efforts was subsistence, which has understandably been of great interest to paleoanthropologists, particularly after 1950 as scientists endeavored to contextualize the fossil remains of distant ancestors. What early humans ate, how food was acquired and processed, even how it was distributed among members of a social group, became viable questions. Throughout the 1950s and 1960s it was widely assumed that the social, cognitive, and technological skills associated with big-game hunting drove the evolution of the human species; in fact the allure of “Man the Hunter” is longstanding in Western thought (Cartmill 1993 ). Raymond Dart, as part of his second foray into human origins studies, proposed that Australopithecus had already developed a hunting strategy facilitated by a technology comprised of durable animal parts that he referred to as the osteodontokeratic (bone, tooth, horn) culture. This concept was enthusiastically embraced by writer Robert Ardrey, who published a series of four popular novels documenting the success of these “killer apes” in the context of a changing environment (e.g., Ardrey 1976 ). Research scientists were only slightly less enthusiastic in championing such ideas (Lee and DeVore 1968 ) which remain popular, if more nuanced today (Wrangham and Peterson 1996 ).

Mirroring changes in the broader society, by the early 1970s some anthropologists challenged the “Man the Hunter” hypothesis and developed an alternative that focused on the central role of women in child rearing and gathering of food resources (Dahlberg 1981 ). These studies used ethnographic data from extant food-foraging societies, the rarity of which injected a sense of urgency on the part of anthropologists. Not long after the “Women the Gatherer” model appeared as a second wave feminist rejoinder to the previously unquestioned authority of “Man the Hunter,” another group of researchers also began to question the big-game hunting scenario. Archeologists, geologists, and paleontologists began working on “site formation processes” to get a better understanding of how assemblages of fragmented animal bones and stone tools came to be commingled. Over the next few decades, often with recourse to modern ecosystems as analogs, one of the main conclusions drawn from the new science called taphonomy (=laws of burial) was the potential importance of scavenging. The association of “bones and stones” was no longer assumed to be the signature of hominid big-game hunting but instead interpreted as meals containing essential fat and protein scavenged by early humans. Perhaps even more disconcerting, some sites were reinterpreted as the remains of carnivore kills occasionally including early humans themselves (Brain 1981 ; Hart and Sussman 2008 ).

Here’s Lucy

If Mary and Louis Leakey’s discoveries at Olduvai put the Great Rift Valley on the map, during the 1970s eastern Africa was validated as the center of early hominid studies. The Leakey’s son Richard established himself on the east side of Lake Turkana in northern Kenya, where his expeditions uncovered a prolific cache of early hominid fossils, some of which corroborated the occasionally controversial claims made by his parents a decade earlier. Sediments around the lake yielded hominid fossils of robust australopithecines, early members of genus Homo , and an early African variant of Asian H. erectus , these days referred to as Homo ergaster (Leakey and Lewin 1978 ). The latter includes a mostly complete skeleton, KNM-WT15000, which has become iconic for the species (Walker and Shipman 1996 ).

Arguably the most significant fossil discovery of the 1970s was another partial skeleton, AL-288, from Hadar, Ethiopia, better known as Lucy (Johanson and Edey 1981 ). Here was a single individual represented by numerous skeletal elements, and although her morphology was generally similar to the “gracile” australopithecines of South Africa, she was even more primitive in some respects. Consequently her discoverers coined a new species name, Australopithecus afarensis that included not only the Hadar specimens but fossils collected by Mary Leakey’s expedition at Laetoli in Tanzania. The latter is renowned for its famous footprint trail preserved in solidified volcanic ash, imparting convincing evidence for bipedalism at 3.6 million years ago. Hadar is also replete with datable volcanic sediments, and Lucy’s status as the most primitive hominid was reinforced by firm radiometric dates which placed the fossils at greater than 3.0 million years ago, at the time astonishingly ancient.

One other significant event from the 1970s bears mentioning. Although the American Journal of Physical Anthropology was first published in 1918, it is perhaps surprising that a journal explicitly dedicated to the study of human evolution did not appear in the U.S. until 1972. Since then the Journal of Human Evolution has been the premier academic forum for publications related to human evolution, and in 1992, the Paleoanthropology Society was established, which organizes its own conference and publishes an online journal.

Modern Human Origins

The question of modern human origins has been debated for centuries, long predating paleoanthropology as a scientific discipline. One of the central issues, which became particularly evident as Renaissance and Enlightenment Europeans began to travel the globe on a regular basis, was how to explain the physical diversity of human populations. Two broad perspectives emerged, one which viewed all people as having a single origin and another which believed that supposedly distinct races had separate origins. The pre-Darwinian debates between so-called monogenists and polygenists were recast with the advent of an evolutionary paradigm in the mid-nineteenth century. Within this new theoretical context, monogenists believed that all living humans evolved from a common ancestor that was already H. sapiens , while the polygenists believed that the races had deeper roots and had descended from different non-modern ancestors (e.g., H. erectus or in a few instances different ape species). A major step towards resolving this debate came in 1987 with an analysis of living human mitochondrial DNA diversity which concluded that H. sapiens had a recent African origin. The discovery of essentially modern human fossils at the 160,000-year-old site of Herto, Ehtiopia, provides paleontological support for a recent African origin, and many subsequent genetic studies have supported this basic conclusion. However, the possibility of some gene flow between migrating early modern humans and local archaic populations remains plausible (compare Stringer and McKie 1996 and Wolpoff and Caspari 1998 , also see Relethford 2003 for a geneticist’s perspective).

Conclusion: Twenty-First Century Paleoanthropology

New fossil discoveries, technological innovations, theoretical advances, and social transformations will continue to inform knowledge of our deep past. Recovery of hominid fossils, some from previously unknown time periods and geographic locations, continues at a brisk rate. Many of the most significant recent discoveries are beginning to fill in the crucial African late Miocene time period during which our lineage ramified from that leading to the chimpanzee (Gibbons 2006 ). Of particular note, one of these fossils was discovered in Chad, quite a distance from established sites in the Great Rift Valley, challenging the long standing hypothesis that hominids evolved in the savanna grasslands of eastern Africa while the African ape ancestors remained sequestered in their tropical rainforest refugium. Moreover, botanical, faunal, and geological evidence associated with very early fossil hominids in Ethiopia and Kenya intimate a forested environment, a discovery that clearly constrains hypotheses explaining the success of the bipedal adaptation.

Other significant fossil discoveries from the early Pleistocene site of Dmanisi in the Republic of Georgia have energized discussion of the initial expansion of early humans beyond the tropics of Africa (Wong 2006 ). Not only are these fossils considerably older than prior known Eurasian specimens, but they are morphologically primitive, especially in terms of stature and cranial capacity, and are associated with very simple (“mode 1”) lithic technology. These early migrants hardly manifest the tall striding bipeds equipped with comparatively advanced Acheulian bifacial tools so often depicted in earlier “out of Africa” scenarios Footnote 3 , which are at least in part based on the iconic WT15000 skeleton mentioned earlier.

Perhaps the most surprising discovery of the last decade is the diminutive 18,000-year-old skeleton from the Indonesian island of Flores, which has sparked a spirited, occasionally acrimonious debate between those advocates of a replacement model of modern human origins and those inclined towards regional continuity (Morwood and van Oosterzee 2007 ). The former, comprised of the team who made the discovery and their allies, interpret the remains as those of a surprisingly primitive hominid akin to early Homo , and perhaps the first documented example of the effects of island dwarfing on an early human population. Other scholars believe the remains to be those of a pathological modern human, whose illness resulted in a cascade of skeletal and dental anomalies. Ongoing research on Flores and other nearby locations will undoubtedly resolve this debate.

New discoveries are not limited to the paleontological record but also include behavioral information gleaned from archaeology. Symbolic expression in the form of language, art (including music), and religion is undoubtedly one of the most distinctive human traits. Evidence for such behavior has proved elusive beyond the seeming cultural explosion perceived in the Upper Paleolithic of Europe beginning around 35,000 years before present. However, archeological evidence for at least some of these behaviors has recently been coaxed out of several sites in sub-Saharan Africa. Advanced utilitarian objects such as blades and harpoons have been recovered well back into the Middle Stone Age and use of ochre and shells for body adornment has been found at sites approaching 100 kiloannum (Balter 2009 ).

Recent advances also include a plethora of technological innovations that have allowed anthropologists to hone traditional inquiries in the areas of dating (e.g., single crystal, laser fusion, argon–argon dating), systematic analysis (e.g., geometric morphometrics), and paleoenvironmental reconstruction (e.g., stable isotope analysis). The badly distorted remains of the spectacular 4.4 megaanum skeleton of Ardipithecus ramidus from Aramis, Ethiopia was restored in part using digital imaging technology (Gibbons 2009 ). Additionally, new technology is facilitating, perhaps even driving, novel questions such as those related to the emergence of the unique human life history pattern.

While fossils provide real-time evidence for human evolution, signals from our ancient past are also encoded into our modern DNA. The groundbreaking work of the 1960s effectively demonstrated our close affinity with the African great apes, and today’s genomic analyses comparing humans and chimpanzees are beginning to reveal differences in much finer detail than heretofore possible. Already several areas within the human genome have been identified as having undergone intense selection; these regions may be related to the evolution of the especially dexterous human thumb, reduction of muscles of mastication in the wake of the ability to cook food, the greatly enlarged neo-cortex, and our ability for spoken language.

In addition to modern DNA analyses, ancient DNA analysis has informed the “Neandertal problem” providing preliminary evidence in support of the replacement hypothesis, at least in Europe, whereby modern humans arriving there equipped with Upper Paleolithic technology drove the indigenous Neandertals to extinction. Even more recent genomic analyses, however, suggest that a small but detectable degree of interbreeding occurred when expanding modern human populations emerging from the African tropics encountered Neandertal populations in the Middle East around 120,000 years before present (Gibbons 2010 ).

In conclusion, our understanding of human origins, like all scientific knowledge, is the result of an ongoing, iterative process. Over the last few decades, the accelerating pace of fossil discoveries and the incorporation of innovative technologies have corroborated and enhanced much of what we already suspected to be true, although there have been a few surprises. No doubt this pattern will continue into the foreseeable future as we slowly, yet inexorably, piece together the circumstances by which our lineage became human.

Hominidae (=hominid) is the biological group (clade) to which humans and their extinct ancestors belong. For many current scholars, this group is distinguished at some lower taxonomic level, usually the tribe Hominini (=hominin). In this study, I maintain the traditional use of Hominidae simply to be consistent with the historical literature. For the same reason, I use the subfamily designation Australopithecinae (=australopithecine) for all of the African “bipedal apes.” This group is certainly paraphyletic, to use the modern jargon, and as a result an increasing number of scholars prefer to use the less formal term australopith to lump together the various African species.

According to the U.S. Census Bureau, there were about 2.2 million students enrolled in U.S. colleges in 1950. That number doubled by 1963 to just less than 4.4 million and doubled again to over 9 million by 1972.

I usually avoid this term despite its heavy usage within the scientific community. I believe that the “Out of Africa” trope perpetuates an anti-Africa bias which seems to suggest that early humans, on several occasions, left Africa wholesale as if there was something inherently undesirable about the place. I suppose that “hominid extra-tropical range expansion” doesn’t have the same ring, but it is more accurate.

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Science and Creationism: A View from the National Academy of Sciences, Second Edition (1999)

Chapter: human evolution, human evolution.

Studies in evolutionary biology have led to the conclusion that human beings arose from ancestral primates. This association was hotly debated among scientists in Darwin's day. But today there is no significant scientific doubt about the close evolutionary relationships among all primates, including humans.

Many of the most important advances in paleontology over the past century relate to the evolutionary history of humans. Not one but many connecting links—intermediate between and along various branches of the human family tree—have been found as fossils. These linking fossils occur in geological deposits of intermediate age. They document the time and rate at which primate and human evolution occurred.

Scientists have unearthed thousands of fossil specimens representing members of the human family. A great number of these cannot be assigned to the modem human species, Homo sapiens. Most of these specimens have been well dated, often by means of radiometric techniques. They reveal a well-branched tree, parts of which trace a general evolutionary sequence leading from ape-like forms to modem humans.

Paleontologists have discovered numerous species of extinct apes in rock strata that are older than four million years, but never a member of the human family at that great age. Australopithecus, whose earliest known fossils are about four million years old, is a genus with some features closer to apes and some closer to modem humans. In brain size, Australopithecus was barely more advanced than apes. A number of features, including long arms, short legs, intermediate toe structure, and features of the upper limb, indicate that the members of this species spent part of the time in trees. But they also walked upright on the ground, like humans. Bipedal tracks of Australopithecus have been discovered, beautifully preserved with those of other extinct animals, in hardened volcanic ash. Most of our Australopithecus ancestors died out close to two-and-a-half million years ago, while other Australopithecus species, which were on side branches of the human tree, survived alongside more advanced hominids for another million years.

Distinctive bones of the oldest species of the human genus, Homo, date back to rock strata about 2.4 million years old. Physical anthropologists agree that Homo evolved from one of the species of Australopithecus. By two million years ago, early members of Homo had an average brain size one-and-a-half times larger than that of Australopithecus, though still substantially smaller than that of modem humans. The shapes of the pelvic and leg bones suggest that these early Homo were not part-time climbers like Australopithecus but walked and ran on long legs, as modem humans do. Just as Australopithecus showed a complex of ape-like, human-like, and intermediate features, so was early Homo intermediate between Australopithecus and modem humans in some features, and dose to modem humans in other respects. The earliest

Early hominids, such as members of the Australopithecus afarensis species that lived about 3 million years ago, had smaller brains and larger faces than species belonging to the genus Homo, which first appeared about 2.4 million years ago. White parts of the skulls are reconstructions, and the skulls are not all on the same scale.

stone tools are of virtually the same age as the earliest fossils of Homo. Early Homo, with its larger brain than Australopithecus, was a maker of stone tools.

The fossil record for the interval between 2.4 million years ago and the present includes the skeletal remains of several species assigned to the genus Homo. The more recent species had larger brains than the older ones. This fossil record is complete enough to show that the human genus first spread from its place of origin in Africa to Europe and Asia a little less than two million years ago. Distinctive types of stone tools are associated with various populations. More recent species with larger brains generally used more sophisticated tools than more ancient species.

Molecular biology also has provided strong evidence of the close relationship between humans and apes. Analysis of many proteins and genes has shown that humans are genetically similar to chimpanzees and gorillas and less similar to orangutans and other primates.

DNA has even been extracted from a well-preserved skeleton of the extinct human creature known as Neanderthal, a member of the genus Homo and often considered either as a subspecies of Homo sapiens or as a separate species. Application of the molecular clock, which makes use of known rates of genetic mutation, suggests that Neanderthal's lineage diverged from that of modem Homo sapiens less than half a million years ago, which is entirely compatible with evidence from the fossil record.

Based on molecular and genetic data, evolutionists favor the hypothesis that modem Homo sapiens, individuals very much like us, evolved from more archaic humans about 100,000 to 150,000 years ago. They also believe that this transition occurred in Africa, with modem humans then dispersing to Asia, Europe, and eventually Australasia and the Americas.

Discoveries of hominid remains during the past three decades in East and South Africa, the Middle East, and elsewhere have combined with advances in molecular biology to initiate a new discipline—molecular paleoanthropology. This field of inquiry is providing an ever-growing inventory of evidence for a genetic affinity between human beings and the African apes.

Opinion polls show that many people believe that divine intervention actively guided the evolution of human beings. Science cannot comment on the role that supernatural forces might play in human affairs. But scientific investigations have concluded that the same forces responsible for the evolution of all other life forms on Earth can account for the evolution of human beings.

While the mechanisms of evolution are still under investigation, scientists universally accept that the cosmos, our planet, and life evolved and continue to evolve. Yet the teaching of evolution to schoolchildren is still contentious.

In Science and Creationism , The National Academy of Sciences states unequivocally that creationism has no place in any science curriculum at any level.

Briefly and clearly, this booklet explores the nature of science, reviews the evidence for the origin of the universe and earth, and explains the current scientific understanding of biological evolution. This edition includes new insights from astronomy and molecular biology.

Attractive in presentation and authoritative in content, Science and Creationism will be useful to anyone concerned about America's scientific literacy: education policymakers, school boards and administrators, curriculum designers, librarians, teachers, parents, and students.

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The Post-liberal Catholics Find Their Man

As vice president, J. D. Vance would elevate their disdain for American liberalism to the highest levels of government.

Produced by ElevenLabs and News Over Audio (NOA) using AI narration.

Updated at 10:24 p.m. ET on August 8, 2024

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When journalists write about ties between Donald Trump and the religious right, they usually focus on evangelical Protestants. That emphasis makes sense, given that evangelicals make up a sizable portion of the GOP’s electoral coalition, and their enduring devotion to the morally and religiously louche Republican nominee remains more than a little shocking.

But Trump’s choice of J. D. Vance as his running mate puts a spotlight on a different faction of the religious right: the so-called post-liberal Catholics, who have been Vance’s friends, allies, and interlocutors since his 2019 conversion to Catholicism (he was raised Protestant) and transformation into a MAGA Republican shortly after.

This group of Catholic intellectuals—which includes Patrick Deneen of Notre Dame, Adrian Vermeule of Harvard Law School, and Sohrab Ahmari, a founder and an editor of the eclectically populist magazine Compact —is known for its sweeping attack on classical liberalism. It claims that a long list of contemporary problems (rising rates of economic inequality, drug addiction, suicide, homelessness, childlessness) can be traced back to moral-philosophical errors made centuries ago by the American Founders and their ideological progenitors. In place of our polity’s commitment to individual rights, autonomy, and pluralism, the post-liberals aim to create a society unified around the common good , which is itself fixed on a theological vision of the Highest Good .

Hence the need for what Deneen calls “regime change” in the title of his most recent book. In concrete terms, this means replacing the people and institutions that dominate America’s cultural, economic, and political life with a new elite willing to eschew liberal norms in service of supposedly higher ideals. In this respect, Vance is the man the post-liberals have been waiting for—a self-identified member of the “post-liberal right,” and now a contender for one of the country’s highest political offices.

Adrian Vermeule: Beyond originalism

Trump and his immediate circle may not share theological convictions with the post-liberals, but the two groups do share certain political impulses. Both exhibit a populist skepticism of elites, deference toward social conservatism, and a preference for putting “America first” when it comes to immigration, trade, labor, and foreign policy. Most of all, Trump and the post-liberals share a willingness, even an eagerness, to smash the entrenched power of the liberal cultural establishment. Vance is the embodiment of these shared hopes and drive for disruption. As vice president in a second Trump administration, he would bring both to the highest levels of government, allowing, for the first time, post-liberal Catholic ideas to exert real political influence.

T hese ambitions mark a significant change in the Catholic right compared with its most recent moment of maximal influence , during the administration of George W. Bush. Then, writers such as Richard John Neuhaus, Michael Novak, and Robert P. George argued that, when properly understood, Catholic Christian revelation, American history and ideals, and the Republican Party’s platform were perfectly harmonious. These thinkers made their case by contending that American liberalism was rooted in theological sources, that Catholic orthodoxy was essentially liberal , and that the GOP was tailor-made to unite the two.

Things feel very different on the Catholic right today. Setbacks at home and at the Vatican—including the election (and reelection) of Barack Obama, Pope Francis’s efforts to push back against the conservative legacies of his predecessors, and the Obergefell decision by the U.S. Supreme Court declaring same-sex marriage a constitutional right—discredited the idea that liberalism and traditional Catholicism could go together. One radical response to these developments can be found on the furthest extreme of the Catholic right, among a group called the integralists. Despite their name, they aim to subordinate the state to the Church, not integrate them.

Vance hasn’t gone that far in his public statements. Yet his account of his conversion to the Catholic Church, published in 2020 in the magazine The Lamp , marks him as very much a man of our post-liberal moment. In his essay, Vance explains the intellectual influences on his spiritual evolution. Some are conventional, such as St. Augustine, the theologian and bishop who has been an inspiration to Christian converts down through the centuries. But one is decidedly less orthodox: the billionaire venture capitalist Peter Thiel.

Before Thiel spent roughly $15 million on Vance’s successful 2022 Senate campaign in Ohio, Vance worked as a principal for Mithril Capital, one of Thiel’s many firms. Their first encounter, however, came back in 2011, when Thiel delivered a talk at Yale Law School, where Vance was then a student. As Vance recalls in his essay, Thiel, who has described himself as Christian, observed that the meritocratic striving of smart young people (like Vance) often results in both personal existential emptiness and societal stagnation. That’s a variation on a critique of liberal democracy that Thiel has been developing for much of his career . In his idiosyncratic reading of Western history, the theological precepts of Christian civilization are what inspired the great scientific and technological achievements of the past several centuries. The ideals of liberal democracy, by contrast, are responsible for the meaninglessness and inertia that supposedly plague the present.

Read: Peter Thiel is taking a break from democracy

Over the decade following his meeting with Thiel, Vance remained broadly committed to a Bush-era vision of continuity between Christianity and the moral outlook and policy agenda of the pre-Trump Republican Party. That earlier Vance favored pro-business economic policy and saw democracy promotion as a crucial element of American foreign policy. He also emphasized the importance of personal character in public life: Poverty could be explained, in part, by moral depravity, and holding political office required integrity. But around the time that he decided to run for the Ohio Senate seat vacated by the retiring Rob Portman in 2021, Vance underwent a second conversion —to the ideas of the post-liberal Catholics and the right-wing populism associated with Donald Trump.

That’s not to say he got more conservative. This new Vance often sounds like Elizabeth Warren, the Democratic senator from Massachusetts, when he talks about economic policy—emphasizing poverty’s structural causes and advocating for a higher minimum wage. On foreign policy, he began defining American interests so narrowly that the fate of a liberal democracy on NATO’s border was a matter of indifference. (“I don’t really care what happens to Ukraine one way or another,” he said in early 2022, shortly before Russia’s invasion.)

Most strikingly, after more than four years of condemning Trump, Vance began defending the former president’s most reckless acts and ambitions. He started denouncing the American “regime” and, in September 2021, told a far-right podcaster that “we are in a late republican period” in which it would be necessary to “get pretty wild, pretty far out there, and go in directions that a lot of conservatives right now are uncomfortable with.” This included “a de-Ba’athification program” with the following directives: “seize the administrative state for our own purposes … fire every civil servant in the administrative state [and] replace them with our people.”

The post-liberal Catholics, including Deneen, in his book on regime change, insist that the moral and political revolution they seek can be accomplished peacefully. But Vance appears ready to excuse some dangerous political brinkmanship. In a recent interview with The New York Times ’ Ross Douthat, Vance defended the idea of states across the country appointing alternative slates of electors after the 2020 election. He seemed to concede that such actions could have precipitated a “constitutional crisis.” So be it.

W hat might be most strange about this unapologetically radical style of politics is how tenuous its ties are to the Catholic Church as an institution and even Christianity as a historical community of faith. Whereas the Bush-era Catholics regularly cited the New Testament, Thomas Aquinas, and John Courtney Murray, today’s post-liberals rarely invoke the Bible or theologians in their political commentary. They don’t base their policy commitments on the Catechism of the Catholic Church . They aren’t in the habit of referring to the social teachings in papal encyclicals. (As with any group, there are exceptions. Ahmari, for example, has cited Catholic teaching in support of political arguments in some works.)

Rather, their theological convictions tend to remain in the background , serving as fuel for something more central to their public thought: a politics of reactionary negation. Their faith confirms that liberalism is the great enemy that must be fought and defeated so that something more wholesome and spiritually invigorating can take its place. But until liberalism has been expunged from the world, Christianity remains mainly a civilizational symbol or identity marker whose public substance is held in abeyance.

Tom Nichols: The moral collapse of J. D. Vance

That’s quite a shift for the Catholic right in a single generation. Not long ago, the group insisted on a near-perfect identification between the Church and American liberalism as expressed by the Republican Party. Now it insists on the discontinuity between Christianity and America’s ruling ideology, which requires nothing short of political revolution to overcome.

Maybe somewhere in between these extremes, a more responsible and enriching form of political engagement for pious Catholics could be found. Regardless, we’re unlikely to see anything resembling such a theological deescalation from J. D. Vance and his post-liberal Catholic allies.

This article originally misidentified The Lamp as an online journal. The article has also been updated to note Sohrab Ahmari’s use of Catholic teaching in his political writing.

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