Primate Rescue Center

The Sexy, Happy Apes We Might Have Been

Erika Fleury May 09, 2016

Something like 2 million years ago, evolution gave the world a gift that's still sitting there wrapped in a bow. The problem is that it was delivered to the wrong address; we humans didn't get it.

The gift has to do with the human family tree, whose ancient trunk and long branches have given rise to many species of ape, many of them long vanished and some, like chimpanzees and gorillas, still with us.

The pivotal evolutionary moment we're concerned with today happened in Africa, when the Congo River formed, thoroughly separating one population of proto-chimpanzees on its south bank. Those to the north became the modern chimps, Pan troglodytes, those to the south became Pan paniscus, bonobos.

And while they look so similar that they weren't recognized as different species until the 1920s, a lot changed. Chimpanzees (whose DNA is nearly identical to humans) are often nasty and competitive. Bonobos are famously friendly and sexy with one another. This striking difference has to do with the status claimed by females.

Jenny is a chimpanzee living at the Primate Rescue Center.

Chimpanzee groups are male-dominated. Chimp dominance is about monopolizing fertile females. While they're dominant, dominant males father a disproportionate number of young. That's the main driver of male competitiveness and aggression. Chimps are jealous, ambitious, sometimes violent even within their group. Male chimps form coalitions to topple dominant males, then share power and privileges.

Contrast bonobos, and here's the thing: the dominant individual is always a female. Female coalitions preserve bonobo peace by keeping males socially submissive. Female authority thoroughly dampens male aggression.

No one knows what selective forces caused two nearly identical apes to develop aggressive male dominance for chimpanzees and peaceful female dominance for bonobos, but to the extent that one can envy a species of ape, I envy bonobos; evolution somehow gave them a gift I wish we'd gotten.

The consequences for how the apes experience life provides a question for us, both silly and profound: which ape would we rather be? After all, we, the strangest of all apes, can consider our choices, right?

Chimpanzees approaching adulthood become less playful, intolerant of sharing. Adult bonobos continue to play with each other the way juvenile chimpanzees play with each other. Bonobos are like chimps who never quite grow up.

Chimpanzee between-group encounters are always tense. They can at times be warlike. Males caught without their own group's support face the strong possibility of lethal violence. Males sometimes kill other groups' babies. (This can sound uncomfortably familiar; as the neurobiologist Lori Marino recently remarked to me, "If you imagine chimpanzees with guns, you realize that's us!")

Contrast bonobos again. When meeting other groups, bonobos often just backtrack into their own territories. And sometimes bonobo groups mingle, flirt, and frolic, using a chance meeting as an opportunity for grooming and horsing around. And if the mood is right they may indulge in a polite — though, by chimpanzee standards, wildly promiscuous — orgy.

Bonobos famously indulge in copious copulatory play, often settling disputes with various nonreproductive sexual configurations. Their sexiness greatly dissipates tensions, facilitating friendly relations within and between groups, food sharing, and cooperation.

In experiments where chimpanzees could not overcome their aggression in order to cooperate in pulling ropes to access a food-filled box, bonobos in the same setup played, foreplayed, and happily shared the treats. Compared to their warmongering, covetous, calculating chimp cousins, bonobos play nice.

Females bonobos call their own shots, choosing whom they wish to mate with and when. And they're not very choosy. Females often initiate sex, and unlike chimps and other mammals, bonobos prefer the belly-to-belly, eyes-to-eyes position.

Female chimpanzees mate only during estrus (that is, when they're in "heat"); female bonobos seem never to glance at their watch. Bonobos seem fully liberated. I call them trisexual; they'll try anything with anybody, anytime they please.

Caring means sharing, and males in bonobo groups sire equivalent numbers of young. And unlike the politically motivated male coalitions of chimpanzees, a bonobo male's closest lifelong bond is with his mother.

Compared with chimpanzees, bonobo brains have more gray matter in regions involved in perceiving others' distress. Bonobos have a larger nerve pathway for controlling aggressive impulses. That's just who they are. It limits stress, dissipates tension, and reduces anxiety to levels that open up room for sex and play and nonviolent living.

The primate expert Richard Wrangham says bonobos seem like "chimpanzees with a threefold path to peace." He enumerates, "They have reduced the level of violence in relations between the sexes, in relations among males, and in relations between communities." Takeshi Furuichi, the only person who has studied both free-living chimps and bonobos, observes, "With bonobos everything is peaceful. When I see bonobos, they seem to be enjoying their lives."

They have their mothers to thank. I like to think we have it in us to ape their gift. It wouldn't hurt.


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