As It Happens

Co-operation may be as inherent to human nature as conflict. Just look at bonobos

Violence between rival factions has long been a part of human history, something we share with our chimpanzee cousins. But some of our other closest genetic relatives, it turns out, are downright collaborative.

Study finds that, unlike chimps, these relatives of humans make peaceful exchange with outside groups

A bonobo holding its baby.
Bonobos commonly co-operate and share with other bonobos outside their core groups, and a new study has determined this phenomenon is 'neither rare nor opportunistic.' (Martin Surbeck)

Violence between rival factions has long been a part of human history, something we share with our chimpanzee cousins. But some of our other closest genetic relatives, it turns out, are downright collaborative.

Bonobos regularly co-operate peacefully with other bonobos outside their core social groups, distinguishing them from their chimpanzee cousins and most other primates — except, perhaps, us.

"People always want to know, OK, were we chimps or were we bonobos? And I think, you know, that's something everybody has to decide for ourselves," Harvard University evolutionary biologist Martin Surbeck told As It Happens host Nil Köksal. 

"I think what we can learn is that it's just not so one-sided — that there is some potential inherent path for warfare, but, you know, there's another side to the coin."

Surbeck is the co-author of a new study about bonobo social behaviour alongside behavioural ecologist Liran Samuni. Their findings, published in the journal Science, shows the friendly primates make a habit of forging outside alliances, sharing resources and exchanging services.

Early-morning grooming session

Surbeck says he remembers the first time he witnessed this co-operation in action about seven years ago near a village in Congo, where the great ape species makes its home.

It was about 3 a.m., and he had trekked out to where a group of bonobos kept their nests high in the canopy and waited "for the sun to come up and the bonobos come down."

Suddenly, he realized there were way more bonobos than usual. Visitors from a neighbouring group had arrived.

About two dozen bonobos, some carrying babies on their backs, perch and move along a network of tree branches.
Bonobos will forge outside alliances to share food and participate in grooming. (Liran Samuni)

There was a lot of bustle and noise among the two groups of bonobos at first, he says. But much to his surprise, they quickly calmed down. Then, they started to pair off and groom each other— a form of social bonding usually reserved for members of their own tight-knit groups. 

He says he immediately thought to himself: "Oh, cool, I want to know more about that."

Matriarchal society 

That peaceful exchange, it turns out, was not a one-time phenomenon. 

Between 2019 and 2021, Martin and Samuni — with the help of local villagers — observed these cross-group interactions again and again. The bonobos forged alliances, picked parasites out of each other's hair, and shared food. 

"They really seem to co-operate with specific individuals, with the individuals who are more likely to somehow return the favours," Surbeck said.

"And it's the individuals that are very good co-operators within the group that reach out and, you know, basically connect different groups."

Most of the time, that means adult females, as bonobos are matriarchal.

University of Victoria primatologist Ammie Kalan, who was not involved in the study, called the findings "remarkable" and says she's curious to learn how much this behaviour extends beyond the bonobos in the study.

Bonobos already have a reputation for being non-aggressive. One 2021 study cited in the research shows that two female bonobos from a different population even went so far as to adopt infants from outside groups

Chimps known for their warfare

This is a far cry from how chimpanzees — which are bonobos' closest relatives — operate in the wild. Humans share a common ancestry with both species.

"Chimpanzee intergroup interactions are extremely aggressive, often involving intergroup killings. These encounters are frequently compared to human warfare," University of Toronto primatologist Julie Teichroeb told CBC in an email.

"These observations may be able to tell us a lot about the beginnings of our own prosocial behaviour and co-operative tendencies, which until now, have not really had a parallel in the behaviour of nonhuman primates."

Laura Bolt, a primatologist at the University of Toronto Mississauga, says the findings "show that social co-operation between individuals belonging to different groups is not unique to humans." She says she's curious to learn how many other social species are more tolerant of outsiders than we know. 

Two adult bonobos and one baby perch on tree branches, their mouths agape.
By studying bonobos, we can better understand our own nature, say primatologists. (Liran Samuni)

Frans de Waal, who studies primate psychology at Atlanta's Emory University, says the study "shoots down a claim common in the anthropological literature" that humans are the only species who co-operate between different groups. He noted that dolphins also exhibit external social networking.

Humans, he says, have a misguided tendency to believe they're unique in the world. 

"It's always the same story, claim after claim about how humans are different, but usually within five to 10 years a claim is debunked."

By better understanding bonobos, Surbeck says we can expand our understanding about who we are and where we came from.

"Constant warfare between groups is not a universal human legacy," Surbeck said.

Rather, he says, it's something "we have to overcome by means of culture" — and there just might be "something in our nature that already enables this."

Corrections

  • An earlier version of this story referred to chimpanzees as ancestors of humans. In fact, humans are not descendants of chimps. Rather, humans, chimps and bonobos all share a common ancestor.
    Nov 21, 2023 1:22 PM ET

Interview with Martin Surbeck produced by Rachel Degasperis

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