Chimps and Bonobos Greet and Bid Farewell to Each Other Much Like Humans Do, New Study Finds

Saying “hello” and “goodbye” are standard human interactions that have never before been identified in non-human species. Until now.

After playing together, these chimps say goodbye much like humans do: they make eye contact and shake hands. Image credit: Raphaela Heesen and Emilie Genty

When we talk to another person, we probably wouldn’t leave without saying goodbye. That would just be impolite. Well, some apes seem to do something similar, according to new research findings. Chimps and bonobos have their own way of greeting and bidding farewell to each another, using signals to begin and end their interactions, IFLScience reports.

The new study, published in the journal iScience, aimed to find out whether chimps, like humans, established some form of obligation when engaging in shared activities. The results could indicate that “joint commitment” evolved before humans did.

The research team was looking for signs of entry and exit phases during chimp and bonobo interactions, in order to establish whether sharing intentions and creating joint commitments was a trait unique to humans, or if it was shared by some other primates, too.

“We were able to launch rockets and land on the moon because we have the ability to share our intentions, which allows us to achieve things so much bigger than a single individual can achieve alone,” first author Raphaela Heesen, a postdoctoral researcher at Durham University, explained in a statement. “This ability has been suggested to be at the heart of human nature.”

Video credit: Raphaela Heesen and Emilie Genty

The research team observed 1,242 natural play (above) and grooming (below) interactions between captive chimpanzees and, separately, captive bonobos. They found that the apes regularly made eye contact and exhibited other communicative signals when they began and ended an interaction with another ape. The scientists believe these signals represent the kind of entry and exit phases practiced among humans when we begin and end a joint commitment.

Video credit: Raphaela Heesen and Emilie Genty

Although both ape species demonstrated these signals, there were some notable differences between them. Bonobos performed hello and goodbye gestures through touching, gazing, holding hands and butting heads prior to playing 90% of the time, compared to 69% for chimps. Bonobos also tended to perform these gestures more often in exit phases (92%), with chimps scoring 86% in this respect.

Also, social bonds seem to affect joint action structure more in bonobos than in chimpanzees. This could mean that these animals might reflect signals in a way that could be compared to “face management” in humans, a theory exploring how we, humans, may alter our expression to make our social interactions smoother.

“When you’re interacting with a good friend, you’re less likely to put in a lot of effort in communicating politely,” Heesen said. This, in turn, could mean that our last common ancestor shares the trait of joint commitment, meaning that it evolved before humans did. That said, further investigation is necessary to be able to tell for sure.

“Behavior doesn’t fossilize. You can’t dig up bones to look at how behavior has evolved. But you can study our closest living relatives: great apes like chimpanzees and bonobos,” Heesen concluded. “Whether this type of communication is present in other species will also be interesting to study in the future.”

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