We all experience stress and conflict — whether it’s an argument with a friend, workplace tension, or competition for resources. But humans aren’t the only ones with coping strategies. Our closest primate relatives, bonobos and chimpanzees, also navigate social tension in pretty surprising ways.
Bonobos, often seen as the “make love, not war” apes, are famous for using sexual behavior to smooth over conflicts. Chimps, on the other hand, have been characterized as more aggressive, relying on dominance and hierarchy to navigate their social world. However, new research suggests these distinctions may not be as clear-cut as we once believed.
In moments of social stress — whether after a fight or during competition for food — both species engage in sexual behaviors to ease tension and maintain group cohesion.
Sexual behavior isn’t just about reproduction. In many species — including humans — it serves roles in social cohesion, stress relief, and conflict resolution. Bonobos are particularly well known for their diverse sexual behaviors, using them in greetings, bonding, and even reconciliation.
Bonobos are the only non-human primates known to engage in tongue kissing. They’re also one of the few animals to engage in face-to-face intercourse. Scientists have long noted that bonobos use sexual contact in ways that closely resemble human social interactions.
Now, researchers wanted to see if chimps engage in similar behaviors.
Bonobos and Chimps in Social Conflict
Scientists observed 53 bonobos (Pan paniscus) at the Lola ya Bonobo sanctuary in Congo and 75 chimpanzees (Pan troglodytes) across two groups at Chimfunshi in Zambia. The scientists analyzed their social interactions in two key contexts: post-conflict situations and pre-feeding tension. Existing science suggests that bonobos use sexual contact more frequently overall. However, in the observed scenario that involved stressful situations, it was chimpanzees that did it more.
The researchers analyzed the five minutes before 45 feeding events. Overall, they recorded 107 instances of genital contact among bonobos and 201 among chimpanzees. This included touching another primate’s genital region with a hand or foot, or direct genital-to-genital contact.
“Whilst bonobos, who are famously hypersexual, were more likely to engage in so-called ‘make up sex’ after periods of conflict, we found that chimpanzees, who some view as our more aggressive cousin, also use sex to ease tensions in many circumstances,” said lead author Jake Brooker, a postdoctoral researcher in the Department of Psychology, Durham University.
“Chimpanzees are known to have a wider repertoire of reassurance behaviours, including body kissing, but sex still constituted a sizeable portion of how they reconciled with each other and their stress-management behaviour.”
A Shared Evolutionary Trait?
Bonobos have long been the “hippie apes,” using sex to solve problems, while chimpanzees were considered the aggressive, warlike cousins. But as this research shows, the reality is far more complex, and far more sexual. Both species use sexual behaviors to navigate social tensions. The differences between them may not be as stark as once thought.
“Against the assumptions of pacifist sex-mad bonobos and aggressive chimpanzees, we found that both species used sex in similar ways during tense situations, including same-sex pairings. This study highlights that beyond reproduction, sex plays an important role in their societies, and most likely for our early ancestors too,” says senior author Professor Zanna Clay also from Durham University.
This could also have implications for human evolution. Humans share a common ancestor with both bonobos and chimpanzees. This study suggests that sociosexual behaviors were likely present in that ancestor.
Of course, humans also use non-reproductive sexual behaviors for many purposes. The overlap in bonobo and chimpanzee behaviors suggests that these functions of sexuality are deeply rooted in our evolutionary past.
“The fact that both species use sex in this way provides a fascinating window back in time, further evidencing that for humans, bonobos and chimpanzees, our use of sex for social reasons is something we have inherited from our common ancestor,” notes Brooker.
“By directly comparing the two species in similar environments during two key situations, we can test the social role of sex in our closest ape relatives, and gain a deeper understanding about how it may have evolved in our own species too,” adds Clay.
A shift in narrative
The study also challenges traditional models of chimpanzee aggression. While chimps are indeed much more aggressive, this research shows that sexuality also plays a role in maintaining social harmony — perhaps more than previously acknowledged.
However, researchers acknowledge that these behaviors were observed in sanctuaries and there could be differences on animals in the wild.
“An exciting next step would be to test the functions of sex further, in different contexts, and to see how much overlap we see between chimpanzee and bonobo sexuality in the wild,” concludes Clay.
Journal Reference: Royal Society Open Science DOI: 10.1098/rsos.242031
