In 1858, in great excitement, Darwin’s acquaintance Alfred Russel Wallace sent him an essay on evolution that accurately summarized the ideas Darwin had been working out privately for twenty years. Darwin had been developing his theories ever since an 1831–36 voyage of scientific discovery on the Beagle, which famously culminated with the young man’s astonished observations of the unique wildlife of the Galapagos Islands. (His adventures became a best-selling travel narrative right away.) Although he was reluctant to publish before building the strongest possible case for his theory of evolution, Darwin quickly decided to present the theory before the Linnean Society in London, giving due credit to Wallace. The theory was out and Darwin put forth a Herculean effort, so that by the following year The Origin of Species appeared in print. This work established Darwin’s scientific trajectory from then on and inspired a controversy that continues to this day.
Certainly, the idea of evolution was “in the air” at midcentury, and it has been a historical truism to say that Darwin’s success was due to the timeliness rather than the originality of his discoveries. But Darwin’s case for evolution became dominant because it was supported by profound scholarship, attention to the best scientific methods known at the time, and voluminous evidence from fossils and live specimens (his membership in an intellectual elite also helped by opening access to these specimens). Darwin asserted that minute variations in a species are “selected” by nature if they are advantageous to individuals in ways that allow them to reproduce more successfully than their fellows. Thus, the new trait is passed on, and over eons a species may accumulate so many of these variations that it transmutes into a new species. A variety or species that does not change will likely die out because the conditions of life inevitably do change.
Darwin refers to a special form of natural selection as “sexual selection,” a process whereby individuals select as reproductive partners other individuals who indicate special fitness, whether through strength, weapons, or ornaments. These attributes enable some individuals (usually males) to win contests for mates (usually females) by appealing to them rather than just relying on brute force. Evolutionary biologists since Darwin have been fascinated by this insight and pursued it from the female’s point of view: a boy lightning bug who flashes more often gets the girl, and the peacock with the most dramatic plumes gets the peahen, in both cases because the female surmises that the extravagant male really does have more stamina and therefore better survival chances and better genes. In Darwin’s scheme, developed at much greater length in The Descent of Man, sexual selection is one aspect of natural selection. Furthermore, such choices might, Darwin suggests, indicate that humans are not the only animals to have an aesthetic sense. However that may be, multiply these natural and sexual selection processes by the millions, and the result is an almost unfathomably long history during which myriads of species arise and then pass away.
A current myth about Darwin is that he delayed publication of The Origin of Species until 1859 because of his personal struggle between the scientific evidence he saw with his own eyes and a commitment to Christian teachings. In his youth, Darwin did prepare for the ministry because he knew that country living would afford him the leisure and setting to pursue his studies in natural history (especially collecting insects). But in matters of religious faith, he had already tended toward agnosticism in the 1830s, while sorting out the implications of the impressive collections he had made, the life-forms he had observed, and the geology he had studied during his five years on the Beagle. After marrying Emma Wedgwood in 1839, Darwin became a dedicated family man, and he regretted differing from his wife on religious matters. But he delayed publishing his findings because he wanted credibility within the tough and increasingly professional scientific community as much as he dreaded giving offense against religious orthodoxy.
Thus, when he published The Origin of Species the year after presenting his and Wallace’s findings before the Linnean Society, Darwin said next to nothing about our fellow simians and left the history of human evolution to be filled in by attentive readers. Darwin was an animal lover, and he was especially fascinated by apes and monkeys, but he wanted his theory to be taken seriously and saw no reason to roil the waters by placing Homo sapiens in the middle of the argument and openly claiming kin with other primates. On the other hand, Darwin’s friend and tenacious defender Thomas Henry Huxley had no such reservations. To this day, many of those who are nervous about evolutionary theory speak of a “Darwinian conspiracy,” a perception that can be attributed to Huxley as the organizer and center of the X Club, which was dedicated to publicizing and popularizing Darwin’s theories and discrediting those who disagreed, especially on religious grounds.
Huxley was a righteous bulldog. In 1863, four years after the appearance of The Origin of Species and somewhat to Darwin’s dismay, he published Man’s Place in Nature, a series of ethnological lectures he had given at the Royal School of Mines. This little volume left nothing about our place in the primate family tree to the imagination. The frontispiece was the now-famous illustration of a Homo sapiens skeleton walking tall at the head of an evolutionary line, followed by various anthropoid skeletons, with a skeletal gibbon last in line. Critical as it was of previous ethnological, paleontological, and biological scientists, the appearance of Huxley’s little book forced the pace of professionalization in the sciences and brought to light the full implications of Darwin’s theory: that humans, too, are animals, in the same family tree as the apes and with no pretensions to a separate creation. According to Huxley, “The question of questions for mankind—the problem which underlies all others, and is more deeply interesting than any other—is the ascertainment of the place which Man occupies in nature and of his relations to the universe of things. Whence our race has come; what are the limits of our power over nature, and of nature’s power over us; to what goal we are tending; are the problems which present themselves anew and with undiminished interest to every man born into the world.”7 Huxley’s pugnacious attitude was especially useful in terms of primatology, in its rudimentary stages an extremely contested discipline, as it is still today. Indeed, primatology is a conflictive disciplinary zone probably for the reason Huxley himself gives: that our relation to nature is the fundamental question and that investigations of nonhuman primates more powerfully (and more viscerally) suggest answers than the pursuit of any other knowledge.
Not only was the taxonomic relationship between humans and other primates contested, but even basic data about apes and monkeys was difficult to collect and unreliable. The great apes, especially, occupied territories almost impossible for Europeans to reach, and the apes feared humans as much as humans feared them, with better reason. Like other field studies during the eighteenth and nineteenth centuries, primatology usually consisted of tracking, shooting, dissection, preservation in kegs of alcohol, and skeletal reconstruction—or killing adult apes in order to capture infants, who usually died in adolescence even if they survived the ocean voyage back to a European zoo. There were a few exceptions among naturalists, but it is worth remembering that, in order to paint them, even John James Audubon killed, mounted, and stuffed the birds he loved. In spite of the tireless collecting done during this period, primate taxonomy remained difficult because the transportation of large specimens, such as the cadavers of great apes, was so challenging that few whole specimens were available. Behavioral studies were next to impossible: few naturalistic primate groupings could be observed in zoos, so data about intraspecies social behavior had to come from field studies, and field biologists