In his view, sex is so central to male primate experience that nonhuman male primates demonstrate an ability to distinguish females of other species from the males. In the second edition of The Descent of Man, Darwin added an account of a male mandrill at the zoo who attempted to bully women visitors into mating. Evidently figuring his best chances for reproductive success, “he was by no means aroused with so great heat by all. Always he chose the younger and picked them out in the crowd and summoned them by voice and gesture.”21 This anecdote evidently so em-barrassed Darwin that he not only placed it in a footnote but wrote it in Latin; presumably, women, who were seldom trained in classical languages, would not be able to read it. (Without denying this particular mandrill’s behavior, I must point out that recent studies show that nonhuman male primate sexual behavior is more often a response to female readiness and that older females are generally more popular than young ones, who have yet to prove their fecundity.)
In animals that reproduce through internal fertilization, of course, males and females have different organs. But Darwin almost always subordinates his discussions of morphology to speculations about process and function. In most primate species, adult males tend to be larger boned, louder, bigger, hairier, and more colorful than adult females. A South African Little Red Riding Hood might have said “What big teeth you have!” to a strapping male chacma baboon instead of a wolf. The question is why. Darwin suggests that sexual dimorphism is apparently unrelated to family structure, whether monogamy or polygamy, and he observes that both kinds of families have occurred in human communities throughout history. (However, the relationship between sexual dimorphism and social reproductive structures is still debated among primatologists today.) What clearly does matter in Darwin’s scheme is sexual selection—that is, a differential in the ability of individuals to pass on their genes. One determiner of sexual selection is male competition for mates; size and strength are useful in a pitched battle. The size and strength that help an individual find mates also help when males take on the role of defending their female and infant conspecifics from predators—a behavior related to reproductive success insofar as it protects a particular male’s progeny or the progeny of his kin.
Maybe big, strong males are more attractive to females even without a fight, especially if they are handsome and musical. Darwin goes into detail about what makes the males of various species sexy. Male primates tend to have more powerful vocal mechanisms, and in most primates with throat pouches, the males’ are bigger than the females’—if the females have them at all. Darwin interprets this feature as an advantage in battles among males for sexual access; as a sexual attraction to females; and, in some species, as an aid to the male in fulfilling his responsibility to protect the females of his group and their young. Likewise, Darwin interprets the large canines and sagittal crests, or cranial reinforcements, of gorillas as defensive advantages that come into play most often during competition for, or protection of, mates. He explains the beards of human males as sexual ornamentation and the relative hairlessness of human females in terms of sexual attractiveness. Similarly, in a long and charmingly illustrated discussion of sexual dimorphism in monkeys, Darwin interprets various puffs, crests, points, and contrasting hair colors in male capuchin, spider, and langur monkeys as sexual ornamentation, useful in attracting females, who are in many primate species the chooser rather than the chosen. Darwin notes the similarity between simians and humans: “Man is more powerful in body and mind than woman, and in the savage state he keeps her in a far more abject state of bondage than does the male of any other animal; therefore it is not surprising that he should have gained the power of selection.”22 This belief accounts for the circular logic implied by the “pornographic” Latin footnote and critiqued by feminists of Darwin’s own time and place: women are not as intelligent as men and therefore should not be trained to read Latin; then, their inability to read Latin suggests a lower degree of intelligence. Darwin was a revolutionary, but he was also a man of his time.
Although Darwin’s science went against the grain of many Victorian prejudices, it was so much a product of the time that his argument on sexual dimorphism in humans is not only anthropocentric and Eurocentric but more convoluted than most of his other work. In this section of his analysis, which covers not geological time but historical time and geographic location, modern civilized women are said to have “evolved” ornamentation by stealing bird plumes and other artificial body extensions to attract men. Humans are therefore different from other primates in the operation of sexual selection. According to Darwin’s theory of sexual selection, in the rest of the primate world (with a few exceptions), males are larger than females because they must fight one another to vanquish rivals and impress the females, who then choose to mate with the victors. The relatively large size of human males cannot be explained in these terms, he claims, because men no longer fight over women. In spite of his diligent research into the reproductive habits of other primate species, Darwin is reduced to special pleading: human males have inherited their relatively large size “from some early male progenitor, who, like the existing anthropoid apes, was thus characterized.”23
Darwin was a poetry lover in his youth and packed Milton in his bag before boarding the Beagle. Nevertheless, he seems to have overlooked the significance of the Victorian fad of inventing and reinventing an epic past in literature, art, architecture, and even home decorating, with fictional heraldry placed above every bourgeois fireplace and suits of armor decorating the entrance hall. One such reinvention was Alfred Tennyson’s Arthurian epic Idylls of the King, published serially between 1859 and 1872, easily the most popular poetic work of the day. Book 10, “The Last Tournament,” was coincidentally published in the same year as The Descent of Man. Like many Victorian works of poetry and song, Idylls of the King is about the chivalric virtues to which Victorians aspired, but almost every plot point involves fighting over women. Men continue to fight over women and bully them into submission even in the twenty-first century, and while most of these battles are conducted with weapons of words or music (Mick Jagger) or money (Donald Trump), that is unfortunately not always the case. To be perfectly fair to Darwin, though, it must be admitted that the complex connections among physiology, behavior, and reproductive success have continued to be one of the most contentious themes in modern primatology, not to mention biology, anthropology, ethnology, sociology, and psychology.
Darwin continued to revise The Origin of Species throughout his life, integrating new information, closing gaps, and answering friendly and unfriendly critics. His theories of natural selection and the struggle for existence—which became known in common parlance as “evolution” and “survival of the fittest”—were soon generally understood and applauded among most of the scientific community.
III
So, in Darwin’s scheme of things, an investigation of species origins necessitates an investigation of sexuality in particular and behavior in general, as well as—one discovers in following Darwin’s train of thought through all of his books—investigations of mind and emotion, not just in humans, not just in primates and other animals, but sometimes even in plants.
It might surprise (or appall) those critics of Darwin who have not studied his work that almost a third of the first volume of The Descent of Man is an impassioned analysis of connections among emotions, mental abilities, and morality in humans and their mammalian kin. Although courtship, mating, and embryonic development are strikingly similar in all mammals, in infancy and adolescence, humans are even more obviously related to apes and monkeys than to other mammals: Darwin points out that monkeys are nearly helpless when they are born and that most orangutans are not mature until they are ten or more years old—not very different from humans in some societies. Consequently, parenting, which in humans is usually institutionalized as motherhood, is essential to the survival of the species. In one of the warmest passages in The Descent of Man, Darwin recounts anecdotes of human-like motherly devotion: a capuchin driving flies away from her infant; a gibbon washing the faces of her children in a stream; captive primate mothers whose grief at losing an infant is so intense that they are suicidal; the adoption of orphan monkeys by unrelated adult females; monkey mothers carefully dividing food among the young; female baboons mentoring the young of other species; even a female baboon who adopts a kitten. (In the first edition of The Descent of Man, Darwin comments on the intelligence displayed by this baboon, who bit off the kitten’s claws after she was scratched. After a critic expressed doubt