One of the persistent myths about the natural world is that animals live in a constant state of aggression, confrontation, and even open combat. But even the relatively brutal chimpanzee spends only about five percent of its day in aggressive encounters—and 20 percent grooming social allies.
The truth is that the social and emotional lives of non-human primates are in many ways a lot like our own, and two new studies add to the growing evidence. In the first, published in Evolution and Human Behavior, researchers found that chimpanzees, like humans, typically form friendships with individuals who have similar personalities. Researchers Jorg J. M. Massen and Sonja E. Koski spent hundreds of hours observing chimpanzee troops at two European zoos, paying particular attention to individuals who liked to sit together. These friends turned out to be similar in sociability based on how much of their time they spent grooming, and whether they liked to hang out in a crowd or off on the periphery. They also resembled each other in boldness (measured by the willingness to mob an apparent threat, like an artificial snake).
That suggests why friendship may matter as much to chimps as to humans: It makes it more likely that individuals will find a mate, reproduce, keep the kids alive, and stay well themselves. Friends also support each other in conflicts. For chimps, as for humans, having friends is natural and necessary. These are social creatures, never meant to live in isolation.
The other study, just out in Proceedings of the National Academy of Sciences, looks at the emotional lives of bonobos, the other species in the chimp’s genus, and thought to be even more closely related to humans. Researchers from Emory University studied bonobos rescued from the bushmeat and pet trades, at a forested sanctuary on the outskirts of Kinshasa in the Democratic Republic of Congo. The emotional life of non-human primates is “still rather a taboo subject in animal behavior,” co-author Zanna Clay told me in an email. Old school researchers suspect it as a form of anthropomorphism—that is, projecting human attributes onto animals.
But Clay and co-author Frans de Waal, a respected primatologist and author, became interested in the topic when they noticed striking differences in how individuals behaved. “Some juveniles were real social stars: They were always dashing about keen to play and groom with everyone,” said Clay. She was particularly impressed by Pole (pronounced Po-lay), ”a brave and very sociable young male, with lots of friends and lots of energy.”
Though bonobos have the reputation of being highly sexually active, their lives are not a perpetual love-in. Conflict is normal, and the celebrated “bonobo handshake” can alternate at times with the bonobo slap in the face. When another bonobo “gave him a whack,” said Clay, Pole shrugged it off. When the same thing happened to less resilient individuals, though, they often worked themselves into a screaming fit. That caused other bonobos to move away.
Pole moved closer instead, even if the victim was “still too worked up to accept the comforting touch,” said Clay. And he often stuck around to hold the victim in a comforting embrace for minutes afterwards. Pole was clearly a master at regulating emotional response to distress—both his own and other bonobos. And that fit the overall pattern. “It seemed to be that the best consolers were also the best ones at regulating social and emotional events overall,” said Clay.
The two researchers realized they were witnessing a phenomenon already well documented in human children: Individuals who are better at regulating their own internal emotions are also better at empathizing with others.
Another element in the new bonobo study matches previous research in humans. As with our own children, what happened to bonobos early in life aslo made a critical difference.
Orphaned young suffered sharp emotional setback, and even though the sanctuary provided a loving caretaker to help rehabilitate each orphan, “there are still some things that only the actual mother is able to provide,” said Clay. These orphans were less likely to recover quickly from stress or console others, and they tended to be more anxious. For instance, they scratched themselves more often, a common means of distracting themselves from stress.
But the researchers also found cause for hope in the way the orphans made an effort at re-building normal social lives. “Our results,” Clay and de Waal write, “demonstrate the striking resilience of these bonobo orphans. The fact that they were able at all to reconcile conflicts, console others, and engage in…play and grooming, suggests that they were managing reasonably in their social world.”
Clay is now deep in the forests of the Congo beginning research to find out if the same emotional patterns she observed among animals in captivity, also play out among bonobos in the wild.