The Descent of Man, and Selection in Relation to Sex
The Descent of Man, and Selection in Relation to Sex is Charles Darwin’s major work applying evolutionary theory to human beings. Darwin argues that humans share common ancestry with other animals and that human mental, moral, and social faculties evolved gradually through natural and, especially, sexual selection. The first volume focuses mainly on establishing humanity’s evolutionary descent, discussing anatomical, embryological, and psychological continuities between humans and other animals, the evolution of morality and religion, and human racial variation. The second volume is largely devoted to a detailed theory of sexual selection, examining how mate choice and competition for mates have shaped secondary sexual characteristics—such as coloration, ornamentation, voice, and behavior—across the animal kingdom and in human populations. The work both consolidates Darwin’s broader evolutionary project and raises controversial claims about sex, race, and civilization that continue to inform, and trouble, discussions of human nature.
At a Glance
- Author
- Charles Darwin
- Composed
- c. 1864–1871
- Language
- English
- Status
- original survives
- •Common Descent of Humans and Other Animals: Darwin argues that humans and other animals share a common ancestry, supported by comparative anatomy, embryology, rudimentary structures, and evidence from atavisms and geographical distribution. The structural and developmental similarities between humans and other primates, particularly the great apes, point to a shared origin rather than separate creation.
- •Continuity of Mental and Moral Faculties: Darwin maintains that there is a fundamental continuity between human mental powers (such as reason, imagination, self-consciousness) and those of other animals, differing largely in degree, not kind. He extends this continuity to moral sentiments, claiming that conscience, sympathy, and a sense of duty evolved from social instincts that confer survival advantages on highly social species.
- •Sexual Selection as a Distinct Evolutionary Force: Darwin systematically defends sexual selection—selection arising from differential success in mating—as a major factor in the evolution of secondary sexual characteristics. Through competition between members of the same sex (intrasexual selection) and mate choice (intersexual selection), traits like bright plumage, elaborate ornaments, displays, and certain behaviors can be favored even when they are otherwise costly.
- •Evolution of Human Sexual Dimorphism and Racial Traits: Darwin applies sexual selection to explain differences between men and women (e.g., greater average male strength, different psychological tendencies) and visible variations among human groups (such as skin color, hair type, and facial features). He hypothesizes that cultural standards of attractiveness and patterns of mate choice over many generations can contribute to the formation and maintenance of these traits, while strongly insisting that all human races belong to a single species.
- •Development and Limits of Moral Progress: Darwin contends that moral progress in human societies arises from the expansion and refinement of social instincts, reason, habit, and the influence of public opinion and education. At the same time, he raises difficult questions about how sympathy and humanitarian behavior can sometimes conflict with “natural” selection, explicitly discussing practices like caring for the weak and the implications for the future evolution of civilized populations.
The Descent of Man is a foundational text in evolutionary biology, anthropology, psychology, and the philosophy of human nature. It articulated one of the first systematic naturalistic accounts of human origins, mental life, morality, and social behavior, embedding humans firmly within a continuous animal spectrum. Darwin’s formulation of sexual selection profoundly shaped later work in evolutionary theory, ethology, and behavioral ecology, and it has been revived and refined in modern evolutionary psychology and sociobiology. At the same time, the book’s reflections on race, gender, and 'civilization' influenced Victorian social thought and became entangled—sometimes directly, sometimes more loosely—with eugenic, racist, and sexist ideologies. As a result, The Descent of Man occupies a complex historical position: both a scientific milestone in understanding human evolution and a source of problematic and contested ideas about human difference.
1. Introduction
The Descent of Man, and Selection in Relation to Sex (1871; 2nd ed. 1874) is Charles Darwin’s major attempt to apply evolutionary theory directly to human beings. Building on On the Origin of Species (1859), it argues that humans share common ancestry with other animals and that the distinctive features of human life—bodily form, mental abilities, morality, and social organization—have arisen through natural processes.
The work is best known for two interconnected claims. First, Darwin maintains the continuity of humans with other animals, anatomically and psychologically, challenging views that treated human beings as categorically separate. Second, he develops a detailed theory of sexual selection to explain traits that seem poorly accounted for by survival-based natural selection alone, including many features of human sexual dimorphism and visible group differences.
As a philosophical and scientific treatise, The Descent of Man has been read both as an extension of Darwin’s biological project and as a wide-ranging reflection on human nature. It has attracted sustained attention not only for its explanations of evolution but also for its treatment of race, gender, morality, and civilization, which later sections of this entry examine from multiple interpretive perspectives.
2. Historical and Scientific Context
When Darwin composed The Descent of Man (c. 1864–1871), debates about evolution had intensified but remained unsettled. On the Origin of Species had made common descent and natural selection central topics in British and European science, yet many supporters of evolution hesitated to apply these ideas to humans.
Scientific Debates
Several intersecting controversies formed the backdrop:
| Topic | Main Positions in Darwin’s Time |
|---|---|
| Human origins | Monogenism (single human species) vs. polygenism (separate origins for “races”) |
| Mechanisms of evolution | Natural selection, Lamarckian inheritance of acquired traits, and various non-Darwinian transformist views |
| Human uniqueness | Sharp mental/moral divide vs. graded continuity with animals |
Figures such as Thomas H. Huxley argued for anatomical continuity between humans and apes, while Alfred Russel Wallace accepted evolution but doubted that natural selection alone could explain human intellect and morality.
Social and Intellectual Milieu
The book also emerged amid Victorian debates over:
- Biblical authority and theology, particularly regarding the special creation of humans
- Abolitionism and racial hierarchy, as imperial expansion and anthropology fueled discussion of human unity and difference
- Gender roles and sexuality, making Darwin’s frank treatment of mate choice and reproductive behavior especially contentious
Scholars often emphasize that The Descent of Man responds to this environment, engaging scientific, religious, and socio-political arguments rather than presenting a purely laboratory-based treatise.
3. Author and Composition
Darwin’s Position and Aims
By the late 1860s, Charles Darwin (1809–1882) was an established, though controversial, scientific author. After Origin, he published works on variation, orchids, and domestic animals, developing ideas about sexual selection and heredity that would be central to The Descent of Man. Proponents suggest he turned explicitly to humans once he judged the general principle of evolution to be sufficiently accepted.
Chronology of Composition
| Year | Milestone related to Descent |
|---|---|
| c. 1864–1868 | Private notebooks and correspondence on human evolution and sexual selection |
| 1868 | Publication of The Variation of Animals and Plants under Domestication; further development of pangenesis and inheritance ideas |
| 1869–1870 | Drafting of The Descent of Man and assembling of vast empirical materials (anecdotes, naturalists’ reports, travelers’ accounts) |
| 1871 | First edition published in two volumes by John Murray |
| 1874 | Revised and expanded second edition issued |
Sources and Method
Darwin combined personal observations, zoological studies, and extensive use of:
- Published travel narratives and missionary reports
- Correspondence with naturalists, physicians, and breeders
- Comparative anatomical and embryological data from contemporaries and predecessors
Supporters view this as an early example of interdisciplinary human science; critics highlight its dependence on uneven and sometimes biased sources, especially regarding non-European peoples and animal behavior.
4. Structure and Organization of the Work
The Descent of Man is organized into three main parts, each with a distinct argumentative focus but linked by the overarching thesis of human evolution.
Overall Layout
| Part | Main Focus | Typical Topics |
|---|---|---|
| Part I | Human descent and characteristics | Anatomy, mind, morality, races, civilization |
| Part II | Sexual selection in animals | Ornaments, weapons, courtship, dimorphism across taxa |
| Part III | Sexual selection in humans; general conclusions | Human sex differences, racial traits, synthesis |
Part I: “The Descent or Origin of Man”
Chapters here argue that humans share a genealogical relationship with other animals. Darwin surveys anatomical homologies, embryology, rudimentary organs, and mental capacities, leading into discussions of moral development, religion, and human races. The chapters are structured to move from bodily to psychological and then social-moral evidence.
Part II: “Sexual Selection”
This long central section develops sexual selection as a general evolutionary process. Arranged largely by taxonomic groups—from insects and fishes through birds to mammals—Darwin presents case studies of secondary sexual characteristics, using them to analyze mechanisms of mate competition and choice.
Part III: “Sexual Selection in Relation to Man, and Conclusion”
The final part applies the framework from Part II to human beings, discussing sexual dimorphism, aesthetic preferences, and human variation, before concluding with a synthetic reflection on human evolution. The organization thus moves from general theory to specific human application, culminating in a broad summary rather than a separate, standalone treatise on ethics or society.
5. Central Arguments and Themes
Several interconnected arguments structure The Descent of Man:
Common Descent and Continuity
Darwin contends that humans share common descent with other animals, particularly the great apes, and that our anatomical and developmental features fit within a broader mammalian pattern. Proponents emphasize his use of comparative anatomy, embryology, and vestigial structures to support this claim.
Mental and Moral Evolution
A central theme is the continuity of mental powers. Darwin argues that faculties such as memory, imagination, and even rudimentary reasoning appear in non-human animals, differing from human capacities in degree rather than kind. He extends this to the moral sense, tracing it to social instincts enriched by language, reflection, and habit.
Sexual Selection
The work develops sexual selection as a complement to natural selection. Darwin proposes that mate competition and choice can favor traits that do not directly improve survival, including ornaments, displays, and behavioral tendencies. He makes this mechanism central to explaining many aspects of animal and human diversity.
Human Variation, Race, and Civilization
Darwin maintains that all humans form a single species, yet he treats racial and cultural differences as outcomes of historical selection, including sexual selection, and environmental influences. He also introduces a narrative of moral and intellectual “progress” linked to social organization and what he terms “civilization,” a theme later readers have interpreted and criticized in different ways.
6. Key Concepts: Sexual Selection, Moral Sense, and Human Variation
Sexual Selection
Darwin distinguishes sexual selection from natural selection:
| Aspect | Natural Selection | Sexual Selection |
|---|---|---|
| Main effect | Differential survival | Differential mating success |
| Favored traits | Survival-enhancing | Mate-attractive or combat-effective |
| Typical outcomes | Camouflage, efficiency | Ornaments, weapons, displays |
Within sexual selection he separates intrasexual competition (often male–male combat) and intersexual choice (often female choice for particular traits). He applies this framework across animals and ultimately to humans.
Moral Sense (Conscience)
Darwin’s moral sense arises, in his account, from:
- Social instincts: tendencies toward sympathy, attachment, and cooperation
- Memory and reflection: capacity to compare past and possible actions
- Language and public opinion: communication of praise and blame
- Habit: internalization of social expectations
Proponents interpret this as a naturalistic genealogy of conscience; critics question whether it adequately captures normativity or moral obligation.
Human Variation
Darwin treats human variation as multi-layered:
- Biological differences (e.g., skin color, hair, facial features) are attributed to a mix of natural selection, sexual selection, and environmental factors over long periods.
- Mental and cultural differences are linked to historical conditions, social structures, and what he calls stages of “civilization.”
He insists on the unity of the human species, while also arranging groups in developmental hierarchies, a tension that has been central to subsequent interpretation.
7. Famous Passages and Controversial Claims
Notable Passages
Commentators often highlight several emblematic moments:
| Theme | Example Passage (approximate location) |
|---|---|
| Human–ape kinship | Part I, Ch. VI, where Darwin insists that humans and higher apes share a close genealogical relationship |
| Humble origins vs. nobility | Part I, Ch. IV, ending, where he reflects on moral elevation compatible with a “lowly” origin |
| Unity of the human species | Part I, Ch. VII, arguing that all “races” belong to a single species |
| Peacock and sexual selection | Part II, Ch. XIII–XIV, on elaborate plumage as a product of mate choice |
| Sympathy and care for the weak | Part I, Ch. V, on humanitarian practices and their relation to selection |
These passages are frequently quoted in discussions of human dignity, evolutionary ethics, and the aesthetics of nature.
Controversial Aspects
Several claims have provoked sustained debate:
- Race and hierarchy: While affirming human unity, Darwin describes some groups as more “civilized” or “advanced,” language many critics read as endorsing hierarchical racial thinking; others argue it reflects, but does not straightforwardly prescribe, Victorian categories.
- Gender and intellect: Darwin suggests average male superiority in certain intellectual domains and presents women as more nurturing and less inventive. Feminist scholars and historians have argued that these claims mirror contemporary gender norms more than robust evidence.
- Moral progress and eugenic themes: His discussion of charity, medicine, and the survival of the “weak” has been interpreted by some as opening the door to eugenic reasoning, though others emphasize his explicit defense of sympathy as a central human virtue.
These issues make The Descent of Man a focal text in debates about the intersection of science, value, and social ideology.
8. Legacy and Historical Significance
The Descent of Man has had a complex and far-reaching impact across disciplines.
Scientific and Philosophical Influence
In evolutionary biology and behavioral science, the work’s elaboration of sexual selection has been foundational. Later research in ethology, behavioral ecology, and evolutionary psychology has variously refined, expanded, or challenged Darwin’s specific proposals while often retaining his basic framework. Philosophers of biology and of mind draw on the book’s arguments about continuity of mental faculties and the naturalistic origins of morality.
Social and Political Reverberations
The text has influenced thinking about race, gender, and social policy in divergent ways. Some interpreters emphasize Darwin’s insistence on the common ancestry and species unity of all humans, situating him as a critic of strict polygenism. Others stress how his language of “higher” and “lower” peoples, and his speculations about hereditary traits, were later cited in support of Social Darwinism and eugenics, even when they exceeded his explicit cautions.
Ongoing Reassessment
Historians, philosophers, and anthropologists continue to reassess the book’s significance:
- Supporters highlight its role in embedding humans within a continuous natural order and pioneering evolutionary studies of behavior and morality.
- Critics underscore methodological limitations, cultural biases, and the work’s entanglement with imperial, racist, and sexist ideologies.
- Alternative readings argue that Darwin’s theory of sympathy and moral progress can be separated from, or even used to critique, later deterministic or hierarchical interpretations.
As a result, The Descent of Man is widely regarded as both a landmark in the scientific study of humanity and a historically situated text whose claims must be interpreted in light of their complex legacy.
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urldate = {December 11, 2025}
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