Shadows of Forgotten Ancestors

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.