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Here we go again. In a few hours, on the eve of another 9/11, another president will make a televised speech to the nation, explaining why he thinks it's necessary to drop American bombs in deserts half-way around the world. In these dark days of perpetual war, it's more important than ever to try to understand the flourishing of peace.
A sudden shift in the course of the Congo river sometime between one and three million years ago split a population of primates that had only recently differentiated from our ancestors. They subsequently evolved in two very different directions. Those on the north side of the river became chimpanzees, while those on the south side became bonobos. These two creatures look very similar, and share almost all their DNA, but their behavior and "culture" differ dramatically. As primatologist Frans de Waal famously summed it up: "Chimps use violence to get sex, while bonobos use sex to avoid violence."
Both species have been studied for decades, both in the wild and in captivity. Over the years, chimpanzee violence has been well-documented: group violence against neighboring troops ("war"), rape, infanticide, murder. But in all these years of observation, not a single instance of a bonobo killing another bonobo has been observed.
How can this be? The most widely-accepted explanation (as far as I know), first offered by Harvard's Richard Wrangham is that because gorillas are also found only on the north side of the river, chimps have to compete with them for some of their food sources, thus leading to more aggression. The bonobos, on the south side, have more plentiful food—since they don't have any gorillas to deal with—and can thus afford to be more relaxed with each other.
But Wrangham's explanation doesn't make sense to me. A few million years is plenty of time for bonobo population to swell to maximum carrying capacity. According to the theory of natural selection, once that happened, individual bonobos would face the same ruthless Malthusian selective pressures as any other species. The struggle for survival would become paramount and they'd face the same competition for food as the chimps do, resulting, theoretically, in the same aggressive behavior.
In River Out of Eden Richard Dawkins articulates this logic so central to mainstream evolutionary theory: "If there ever is a time of plenty, this very fact will automatically lead to an increase in the population until the natural state of starvation and misery is restored."
So, if Wrangham's explanation doesn't hold water, how can we explain the mysterious peacefulness of the bonobo? The best explanation I can think of is cultural. Some (most) scientists would probably be uncomfortable talking about non-human culture, but what else shall we call it when groups of the same species adopt differing behavioral patterns that they pass on to their descendants? For example, chimps in some areas of Africa know how to use a stone to open a particular kind of nut, while chimps in other areas walk past the same nuts without a clue. Is this not culture?
Nonhuman primates offer intriguing evidence of the “soft power of peace.” Frans de Waal and Denise Johanowicz devised an experiment to see what would happen when two different macaque species were placed together for five months. Rhesus monkeys (Macaca mulatta) are aggressive and violent, while stump-tails (Macaca arctoides) are known for their more chilled-out approach to life. The stump-tails, for example, make up after conflict by gripping each other’s hips, whereas reconciliations are rarely witnessed among rhesus monkeys.
Once the two species were placed together, however, the scientists saw that the more peaceful, conciliatory behavior of the stump-tails dominated the more aggressive rhesus attitudes. Gradually, the rhesus monkeys relaxed. As de Waal recounts, “Juveniles of the two species played together, groomed together, and slept in large, mixed huddles. Most importantly, the rhesus monkeys developed peacemaking skills on a par with those of their more tolerant group mates.”
Even when the experiment concluded, and the two species were once again housed only with their own kind, the rhesus monkeys were still three times more likely to reconcile after conflict and groom their rivals.
A fluke? Neuroscientist/primatologist Robert Sapolsky has spent decades observing a group of baboons in Kenya, starting when he was a student in 1978. In the mid-1980s, a significant proportion of adult males in the group abruptly died of tuberculosis they’d picked up from infected food in a dump outside a tourist hotel. But the prized (albeit infected) dump food had been eaten only by the most belligerent, high-status baboons (think: Wall Street and inside the D.C. beltway), who had driven away less aggressive males, females, or juveniles.
With all the hard-ass males gone, the laid-back survivors found themselves suddenly in charge. The defenseless troop would seem to have been easy pickings for baboon pirates: a whole troop of females, sub-adults, and easily cowed males just waiting to be raped and pillaged. Because male baboons leave their natal troop at adolescence, within a decade of the dump cataclysm, none of the original, atypically mellow males were still around. But, as Sapolsky reports, “the troop’s unique culture was being adopted by new males joining the troop.”
In 2004, Sapolsky reported that two decades after the tuberculosis “tragedy,” the troop still showed higher-than-normal rates of males grooming and affiliating with females, an unusually relaxed dominance hierarchy, and physiological evidence of lower-than-normal anxiety levels among low-ranking males—who would normally be totally stressed-out in typical baboon troops. Even more recently, Sapolsky told me that as of his most recent visit, the troop’s unique culture appeared to be intact. (Watch Sapolsky discuss this episode here.)
To me, a cultural explanation for primate peace is far more parsimonious, interesting, and hopeful than an explanation based on resource scarcity or the presence of gorillas. To me, these cases demonstrate that thinkers from Buddha to Gandhi to M.L. King, to Mandela were right: a culture of peace can overcome violence.
(Parts of this were adapted from Sex at Dawn).
