A Natural History of Peace

Robert M. Sapolsky

From Foreign Affairs, January/February 2006

Summary:  Humans like to think that they are unique, but the study of other primates has called into question the exceptionalism of our species. So what does primatology have to say about war and peace? Contrary to what was believed just a few decades ago, humans are not "killer apes" destined for violent conflict, but can make their own history.

Robert M. Sapolsky is John A. and Cynthia Fry Gunn Professor of Biological Sciences and Professor of Neurology and Neurological Sciences at Stanford University. His most recent book is "Monkeyluv: And Other Essays on Our Lives as Animals."

PAX BONOBO

Primatology has long been dominated by studies of the chimpanzee, due in large part to the phenomenally influential research of Jane Goodall, whose findings from her decades of observations in the wild have been widely disseminated. National Geographic specials based on Goodall's work would always include the reminder that chimps are our closest relatives, a notion underlined by the fact that we share an astonishing 98 percent of our DNA with them. And Goodall and other chimp researchers have carefully documented an endless stream of murders, cannibalism, and organized group violence among their subjects. Humans' evolutionary fate thus seemed sealed, smeared by the excesses of these first cousins.

But all along there has been another chimp species, one traditionally ignored because of its small numbers; its habitat in remote, impenetrable rain forests; and the fact that its early chroniclers published in Japanese. These skinny little creatures were originally called "pygmy chimps" and were thought of as uninteresting, some sort of regressed subspecies of the real thing. Now known as bonobos, they are today recognized as a separate and distinct species that taxonomically and genetically is just as closely related to humans as the standard chimp. And boy, is this ever a different ape.

Male bonobos are not particularly aggressive and lack the massive musculature typical of species that engage in a lot of fighting (such as the standard chimp). Moreover, the bonobo social system is female dominated, food is often shared, and there are well-developed means for reconciling social tensions. And then there is the sex.

Bonobo sex is the prurient highlight of primatology conferences, and leads parents to shield their children's eyes when watching nature films. Bonobos have sex in every conceivable position and some seemingly inconceivable ones, in pairs and groups, between genders and within genders, to greet each other and to resolve conflicts, to work off steam after a predator scare, to celebrate finding food or to cajole its sharing, or just because. As the sound bite has it, chimps are from Mars and bonobos are from Venus.

All is not perfect in the bonobo commune, and they still have hierarchies and conflict (why else invent conflict resolution?). Nonetheless, they are currently among the trendiest of species to analyze, a wonderful antidote to their hard-boiled relatives. The trouble is, while we have a pretty good sense of what bonobos are like, we have little insight into how they got that way. Furthermore, this is basically what all bonobos seem to be like -- a classic case of in-their-nature-ness. There is even recent evidence for a genetic component to the phenomenon, in that bonobos (but not chimps) possess a version of a gene that makes affiliative behavior (behavior that promotes group cohesion) more pleasurable to males. So -- a wondrous species (and one, predictably, teetering on the edge of extinction). But besides being useful for taking the wind out of we-be-chimps fatalists, the bonobo has little to say to us. We are not bonobos, and never can be.

WARRIORS, COME OUT TO PLAY

In contrast to the social life of bonobos, the social life of chimps is not pretty. Nor is that of rhesus monkeys, nor savanna baboons -- a species found in groups of 50 to 100 in the African grasslands and one I have studied for close to 30 years. Hierarchies among baboons are strict, as are their consequences. Among males, high rank is typically achieved by a series of successful violent challenges. Spoils, such as meat, are unevenly divided. Most males die of the consequences of violence, and roughly half of their aggression is directed at third parties (some high-ranking male in a bad mood takes it out on an innocent bystander, such as a female or a subordinate male).

Male baboons, moreover, can fight amazingly dirty. I saw this happen a few years ago in one of the troops I study: Two males had fought, and one, having been badly trounced, assumed a crouching stance, with his rear end up in the air. This is universally recognized among savanna baboons as an abject gesture of subordination, signaling an end to the conflict, and the conventional response on the part of the victorious male is to subject the other to a ritualized gesture of dominance (such as mounting him). In this instance, however, the winner, approaching the loser as if to mount him, instead abruptly gave him a deep slash with his canines.