Warrior Baboons Give Peace a Chance

Born violent? A troop of baboons chooses an enduring culture of peace.
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The evolutionary biologist Theodosius Dobzhansky once said, “All species are unique, but humans are uniquest.” Humans have long taken pride in their specialness. But the study of other primates is rendering the concept of such human exceptionalism increasingly suspect.

We now know, for example, that other species invent tools and use them with dexterity and local cultural variation. Other primates display “semanticity” (the use of symbols to refer to objects and actions) in their communication in ways that would impress any linguist.

Our purported uniqueness has been challenged most, however, with regard to our social life. Like the occasional human hermit, there are a few primates that are typically asocial (such as the orangutan). Apart from those, however, it turns out that one cannot understand a primate in isolation from its social group. Humans are just another primate with an intense and rich social life—a fact that raises the question of whether primatology can teach us something about a rather important part of human sociality, war and peace.

Robert Sapolsky

Baboons are exceptional subjects for studying social stress, behavioral scientist Robert Sapolsky says, because they usually live in large, complex groups with plenty of food and few predators. They therefore devote minimal time to surviving and have ample free time to make life miserable for each other.

It used to be thought that humans were the only savagely violent primate. That view fell by the wayside in the 1960s as it became clear that some other primates kill their fellows aplenty. Males kill; females kill. Some kill one another’s infants with cold-blooded stratagems worthy of Richard III. Some use their toolmaking skills to fashion bigger and better cudgels. Some other primates even engage in what can only be called warfare—organized, proactive group violence directed at other populations.

As field studies of primates expanded, what became most striking was the variation in social practices across species. Yes, some primate species have lives filled with violence, frequent and varied. But life among others is filled with communitarianism, egalitarianism, and cooperative child-rearing.

The most disquieting fact about the violent species was the apparent inevitability of their behavior. Certain species seemed simply to be the way they were, fixed products of the interplay of evolution and ecology, and that was that.

After decades more work, the picture has become quite interesting. Some primate species, it turns out, are indeed simply violent or peaceful, with their behavior driven by their social structures and ecological settings. More important, however, some primate species can make peace despite violent traits that seem built into their natures.

Pax Bonobo

Primatology has long been dominated by studies of the chimpanzee, due in large part to the phenomenally influential research of Jane Goodall. National Geographic specials based on Goodall’s work would always include the reminder that chimps are our closest relatives. Goodall and other chimp researchers have carefully documented an endless stream of murders, cannibalism, and organized group violence among their subjects.

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 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.

Primate species with some of the most aggressive and stratified social systems have been seen to cooperate and resolve conflicts—but not consistently ...

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.

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. 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

Robert Sapolsky video still
Video: Robert Sapolsky
What can we learn from our similarities and differences in relation to other animals?

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. 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).

Primate species with some of the most aggressive and stratified social systems have been seen to cooperate and resolve conflicts—but not consistently, not necessarily for benign purposes, and not in a cumulative way that could lead to some fundamentally non-Hobbesian social outcomes. The lesson appears to be not that violent primates can transcend their natures, but merely that the natures of these species are subtler and more multifaceted than previously thought. At least that was the lesson until quite recently.


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baboon photo by Natalie Manuel

Photo by Natalie Manuel.

Left Behind

In the early 1980s, “Forest Troop,” a group of savanna baboons I had been studying—virtually living with—for years, was going about its business in a national park in Kenya when a neighboring baboon group had a stroke of luck. Its territory encompassed a tourist lodge that expanded its operations and, consequently, the amount of food tossed into its garbage dump. Baboons are omnivorous, and “Garbage Dump Troop” was delighted to feast on leftover drumsticks, half-eaten hamburgers, remnants of chocolate cake, and anything else that wound up there. The development produced nearly as dramatic a shift in the social behavior of Forest Troop. Each morning, approximately half of its adult males would infiltrate Garbage Dump Troop’s territory, descending on the pit in time for the day’s dumping and battling the resident males for access to the garbage. The Forest Troop males that did this shared two traits: they were particularly combative (which was necessary to get the food away from the other baboons), and they were not very interested in socializing (the raids took place early in the morning, during the hours when the bulk of a savanna baboon’s daily communal grooming occurs).

Soon afterward, tuberculosis, a disease that moves with devastating speed and severity in nonhuman primates, broke out in Garbage Dump Troop. Over the next year, most of its members died, as did all of the males from Forest Troop who had foraged at the dump. The results were that Forest Troop was left with males who were less aggressive and more social than average, and the troop now had double its previous female-to-male ratio.

Within a few years, members of the species demonstrated enough behavioral plasticity to transform a society of theirs into a baboon utopia.

The social consequences of these changes were dramatic. There remained a hierarchy among the Forest Troop males, but it was far looser than before. Aggression was less frequent, particularly against third parties. And rates of affiliative behaviors, such as males and females grooming each other or sitting together, soared. There were even instances, now and then, of adult males grooming each other—a behavior nearly as unprecedented as baboons sprouting wings.

This unique social milieu did not arise merely as a function of the skewed sex ratio. Other primatologists have occasionally reported on troops with similar ratios but without a comparable social atmosphere. What was key was not just the predominance of females, but the type of male that remained. The demographic disaster—what evolutionary biologists term a “selective bottleneck”—had produced a savanna baboon troop quite different from what most experts would have anticipated.

But the largest surprise did not come until some years later. Female savanna baboons spend their lives in the troop into which they are born, whereas males leave their birth troop around puberty; a troop’s adult males have thus all grown up elsewhere and immigrated as adolescents. By the early 1990s, none of the original low aggression/high affiliation males of Forest Troop’s tuberculosis period was still alive; all of the group’s adult males had joined after the epidemic. Despite this, the troop’s unique social milieu persisted—as it does to this day, some 20 years after the selective bottleneck. As defined by both anthropologists and animal behaviorists, “culture” consists of local behavioral variations, occurring for nongenetic and nonecological reasons, that last beyond the time of their originators. Forest Troop’s low aggression/high affiliation society constitutes nothing less than a multigenerational benign culture.

Natural Born Killers?

Are there any lessons to be learned here that can be applied to human-on-human violence—apart, that is, from the possible desirability of giving fatal cases of tuberculosis to aggressive people? 

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In the early 1960s, a rising star of primatology, Irven DeVore, of Harvard University, published the first general overview of the subject. Discussing his own specialty, savanna baboons, he wrote that they “have acquired an aggressive temperament as a defense against predators, and aggressiveness cannot be turned on and off like a faucet. It is an integral part of the monkeys’ personalities, so deeply rooted that it makes them potential aggressors in every situation.” Thus the savanna baboon became, literally, a textbook example of life in an aggressive, highly stratified, male-dominated society. Yet within a few years, members of the species demonstrated enough behavioral plasticity to transform a society of theirs into a baboon utopia.

The first half of the twentieth century was drenched in the blood spilled by German and Japanese aggression, yet only a few decades later it is hard to think of two countries more pacific. Sweden spent the 17th century rampaging through Europe, yet it is now an icon of nurturing tranquility. Humans have invented the small, nomadic band and the continental megastate and have demonstrated a flexibility whereby uprooted descendants of the former can function effectively in the latter. We lack the type of physiology or anatomy that in other mammals determine their mating system, and have come up with societies based on monogamy, polygyny, and polyandry. And we have fashioned some religions in which violent acts are the entrée to paradise and other religions in which the same acts consign one to hell. Is a world of peacefully coexisting human Forest Troops possible? Anyone who says, “No, it is beyond our nature,” knows too little about primates, including ourselves.

Excerpted from “A Natural History of Peace” in Volume 85, Number 1 of Foreign Affairs. Used with permission.


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