When a group of chimpanzees knows food is coming, something remarkable happens before anyone takes the first bite. They gather close, touch each other's faces, embrace, and sometimes place a finger gently inside each other's mouths. Not out of aggression — but out of solidarity.
That's the finding of a new study from Durham University, published this week, which reveals that great apes use deliberate physical contact to build trust and reduce conflict before stressful situations. And according to the researchers, this behavior may be one of the oldest social tools in the primate playbook — dating back at least seven million years, before humans, chimpanzees, and bonobos shared a common ancestor.
The researchers, led by Professor Zanna Clay, studied chimpanzees and bonobos at two great ape sanctuaries — Lola ya Bonobo in the Democratic Republic of Congo and Chimfunshi Wildlife Orphanage Trust in Zambia. Both species were put in a simple but revealing situation: they knew peanuts were on their way, triggering social tension as group members jostled for position.
Scientists observed each group for five minutes before the food arrived, recording every instance of touching, embracing, and kissing. What they found was striking: individuals who engaged in reassuring physical contact before the food arrived were significantly more likely to actually get food — and to eat peacefully alongside their companions.
In more tolerant groups, "reassurance trains" emerged — chains of individuals embracing each other in sequence, spreading calm through the group like a wave. Chimpanzees, despite their reputation for aggression, also participated in close contact, including placing fingers gently in each other's mouths — a profound display of trust between animals who could easily bite.
"Before stressful events, they come together, they reassure each other, they touch each other, they hug each other," Professor Clay said. "It's like a 'we' rather than a 'me.'"
Dr. Jake Brooker, a co-author of the study, noted that this behavior has deep evolutionary roots. "Comparing bonobos and chimpanzees — our two closest relatives — offers fascinating insight into the evolutionary roots of social behavior and how they, and we, manage tension, competition, and cooperation," he said.
The study suggests that social touch isn't a modern invention or even a uniquely human behavior. It appears to be an ancestral strategy, conserved across millions of years of primate evolution, for turning potential conflict into cooperation.
Think about a sports team huddling before a match, or a colleague squeezing someone's shoulder before a tough presentation. Scientists now believe those gestures draw on the same social toolkit used by apes seven million years ago.
"Social touch is one of the oldest forms of communication and likely predated language," Dr. Brooker noted. That makes the human instinct to reach for another person before walking into a stressful situation not culturally acquired — but evolutionary. Written into our biology, and shared with our closest relatives.
The researchers say the implications extend beyond primatology. More tolerant groups showed higher levels of reassuring contact — and better outcomes in terms of peaceful food-sharing. The more a group nurtures its social bonds before moments of stress, the better it functions. That's as true for chimpanzees in Zambia as it is for humans anywhere on Earth.
