But the gregariousness of the primates is one of their hallmarks. Mutual aid in working both sides of the predator/prey relationship and in conflict with other groups of the same species is widespread, not just among the primates, but among most mammals and birds.
While selfishness, exploitation, and trade are commonplace in chimpanzee society, we cannot use this fact along with our kinship with chimps to justify laissez faire economics. Nor can we use it to discredit free market societies on the grounds of their being ape-like.* Cooperation, friendship, and altruism are also chimp traits, but this is not an argument for some competing socialist economic doctrine. Recall the macaques who would rather go hungry than administer an electric shock to other, not closely related macaques—going so far as to reject even substantial material incentives. Is this a rebuke to advocates of capitalism? At least as far back as Aesop, animal behavior has been used to buttress this or that economic theory. Even in our ideological debates, we make the other animals work for us.
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“Man is a social animal,” wrote Aristotle, or, as it is sometimes translated, “Man is a political animal.” This was meant to be characteristic of humans, but not defining; again, a necessary but not a sufficient condition. The subtle and volatile factionalism of chimp and bonobo societies shows how far off the mark this is as a distinction of humanity. The social insects—ants, bees, termites—have much better organized and much more stable social structures than humans. Particular aspects of human social behavior fare no better, although a great many such definitions have been proposed: For example, humans tenderly cherish their young, but so do most other mammals and birds.
“Courage is the peculiar excellence of man,” Tacitus recorded the Roman aristocrat Claudius Civilis as saying.14 Even if the heroic exploits of mother birds shamming a broken wing, or of elephants and chimps saving their young from predators or rushing water, or of the beta hind staring the wolf in the eye so her companions can escape—even if such examples were unknown in the time of this Claudius, didn’t he know about dogs? He was put in chains and brought before Nero. History does not record how much of the “peculiar excellence” was available to him in his hour of need.
Another ancient definition of humans, tracing back to Aristotle, is a “rational animal.”15 This is the distinction pointed to by many of the key figures in Western philosophy. But the categorizing chimps, reasoning by analogy and transitive inference, the conversing bonobos, and the culturally innovative macaques remind us that other animals reason also; not as well as the great Western philosophers, to be sure—but the philosophers believed not in a difference of degree, but in a radical difference in kind.
“[M]an differs from irrational creatures in this, that he is master of his actions,” was a tenet of St. Thomas Aquinas in his Summa Theologica. But are we “masters” of our actions always and in all circumstances? Do other animals never exhibit “mastery”? In giving, as was his practice, selected pros and cons for the propositions discussed, Aquinas—debating “whether choice is to be found in irrational animals?”—mentions a case where a stag at a crossroads seemed to choose one path by excluding the alternatives. This is rejected as evidence of choice because “choice properly belongs to the will, and not to the sensitive appetite which is all that irrational animals have. Therefore, irrational animals are not able to choose.” He also held that “irrational animals” could not command, “since they are devoid of reason.” All this may have satisfied generations of philosophers, and established a tradition that influenced Descartes, but is it not clear that Aquinas—consider his starting point of “irrational animals”—was begging the question, assuming what he was trying to prove?16
“Actions directed towards a goal do not occur in any other animals at all,” in a like vein wrote Jakob von Uexküll, a once influential expert on animal behavior.17 But we need only think of the chimp holding a club behind his back and searching for his rival, or collecting stones to throw at an enemy, or the female prying his fingers open and removing the stones, to realize how much in error such statements are.
For the philosopher John Dewey, what distinguishes us is memory:With the animals, an experience perishes as it happens, and each new doing or suffering stands alone. But man lives in a world where each occurrence is charged with echoes and reminiscences of what has gone before, where each event is a reminder of other things.18
This claim is manifestly untrue for many animals, and chimps above all live in a world “charged with echoes and reminiscences.” The cat experiencing a hot stove avoids the stove thereafter; elephants and deer soon grow wary of hunters; dogs who have been beaten cower when the rolled-up newspaper is raised; even worms, even one-celled protozoa can be taught to run a simple maze. The dominance hierarchy is a frozen memory of past coercion. How oblivious of the real life of nonhuman animals is Dewey’s attempt to define us!
Many human sexual practices have been thought to be defining. Maybe it’s kissing: “Only mankind kisses. Only mankind has the reason, the logic, the happy faculty of being able to appreciate the charm, the beauty, the extreme pleasure, the joy, the passionate fulfilment of the kiss!” rhapsodizes a small book on the subject.19 But chimps routinely and exuberantly kiss.
Maybe what’s special about us is our reproductive posture: “It seems plausible to consider that face-to-face copulation is basic to our species.”20 But face-to-face copulation is common among the bonobos.
Concealed ovulation and female orgasm21 have been thought unique to humans, but bonobos do not garishly advertise their ovulations, and female chimps, bonobos, stumptail monkeys and, probably, many other primate females have orgasms—as determined in part by equipping them with physiological sensors before they mate, in the style of an experiment by Masters and Johnson.
Maybe it’s our mode of sexual coercion: “That rape … is an exclusively human character seems to be beyond serious doubt,” opined a scientist writing on primates in 1928.22 But rape is known among orangutans and stumptails, violent sexual coercion is a commonplace among baboons and chimps, and the doubt is serious indeed.
Maybe it’s the elaboration and duration of our sexual foreplay; in this at least some humans may lead the other primates.23 But this is learned behavior, as the prevalence of premature ejaculation, especially among adolescent boys, and the self-taught ability of many men to postpone ejaculation make clear. In the integration of sexual acts into everyday social life humans are probably down toward the bottom of the primate list. Most human cultures demand that even socially condoned sexual behavior be carried on in private;24 we can see something of the sort in chimp consortship, and in clandestine encounters out of sight of the dominant males.
Maybe our distinction is the traditional and striking gender-specific division of labor: The men hunt and fight; the women gather and nurture.25 But this cannot be a defining characteristic, because chimps have a similar division of labor: Patrols, group defense, and throwing missiles are all mainly male responsibilities; caring for the young and using tools to crack open nuts are mainly female responsibilities. Also, women’s and men’s jobs are in our time becoming increasingly indistinguishable.
Our long childhood, the years between birth and puberty, is essential for our education, but it is not as long as an elephant’s; and the progressively earlier arrival of sexual maturity in the human life cycle over the last few centuries is whittling down our childhood so that it is now only a little longer than the chimpanzees’ (who sexually mature around age ten). Play is so central to our growing up that it was once suggested26 to call our species Homo ludens (“the man who plays”). But play can be seen throughout the mammalian class, especially when maturity is long delayed.