Shadows of Forgotten Ancestors

The nineteenth-century philosopher and theologian Ludwig Feuerbach—known for his influence on Karl Marx—proposed that the distinction of humans is recognition of ourselves as a species.³⁵ But many animals readily distinguish members of their own species from members of all others—for example, through olfactory cues. And humans are notable for demonizing members of their own species, declaring them less than human, to disinhibit sanctions on murder—especially during wartime.

Humans are sometimes said to be better at making class distinctions than other primates are,³⁶ but primate dominance hierarchies, some of them hereditary, seem to embrace a fineness of social discrimination that in some respects exceeds even our own.

We conclude that none of these sexual and social traits seem to work as defining characteristics of the human species. The behavior of other animals, especially the chimps and bonobos, renders such pretensions specious. They are just too much like us.

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Knowledge and behavior patterns that are not hardwired into our genetic material, but rather are learned and passed on within a given group from generation to generation, are called culture. Could culture be the defining mark of humanity?

“Culture,” says a major article in The Encyclopaedia Britannica,is due to an ability possessed by man alone The question of whether the difference between the mind of man and that of the lower animals is one of kind or of degree has been debated for many years, and even today [1978] reputable scientists can be found on both sides of this issue. But no one who holds the view that the difference is one of degree has adduced any evidence to show that non-human animals are capable, to any degree whatever, of a kind of behaviour that all human beings exhibit.

The author then gives three examples of behavior that he thinks characterizes humans, and concludes, “There is no reason or evidence that will lead one to believe that any animal other than man can have or be brought to any appreciation or comprehension whatever of such meanings and acts.”³⁷

And what are these three examples? One is “defining and prohibiting incest.” But this prohibition, at least for the father-daughter and mother-son varieties, is, as we’ve described, prevalent, indeed nearly invariable, among the primates—who have elaborate conventions to guarantee high levels of outbreeding. The taboo applies to many other animals as well. In studying Kenyan birds known as bee-eaters, the biologist Stephen Emlen carefully noted the identity and behavior of each bird; in eleven years of work he was unable to find even a single case of incest, either between siblings or between parent and offspring. (The other two examples given in the Britannica

article are “classifying one’s relatives and distinguishing one class from another,” which chimps do well enough—at least for mother-child and sibling kinship—and “remembering the sabbath to keep it holy,” which is an institution unknown in many human cultures.)

Despite the common description of the incest prohibition as a taboo—that is, learned—it seems to be, to a considerable degree, innate. It serves as a hereditary ethical proscription, evolved for good genetic reasons, and reinforced by the conventions and rules of society (although, for all that, functioning imperfectly—very imperfectly in civilized society).

Clearly chimps have at least the rudiments of culture. In different forests, they must deal with different local geographies and ecologies. They remember over weeks—maybe over years—termite mounds, drumming trees, or, in one account, the site of a noteworthy combat. Such matters are common knowledge. Each group, with its own terrain and its own sequence of historical events, has its own miniature culture. Mutually isolated groups of chimps have different conventions in fishing for termites or driver ants, in using leaves as sponges for soaking up drinking water, in how they hold on to each other during grooming, in some aspects of the gestural language of courtship, and in hunting protocols.³⁸ And thanks to Imo, the macaque genius who figured out how to separate the wheat from the sand, we even have some insight into the emergence and spread of new discoveries and new cultural institutions among the primates.