Saying “hello” and “goodbye” is pretty standard in human interactions, but such behavior has never before been identified in a non-human species, that is, until now. New research has found that chimps have their own way of greeting and bidding farewell to one another, using signals to begin and end their interactions.
The new study, published in the journal iScience, looked at the “joint commitment” between chimps to see if, like humans, they established some form of obligation when engaging in shared activities. Getting together is common among social animals, but the team on the study were looking for signs of entry and exit phases during chimp and bonobo hangouts, to try and ascertain if sharing intentions and creating joint commitments was a trait unique to humans, or if it was shared by some of our closest relatives.
“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,” said first author Raphaela Heesen, a postdoctoral researcher at Durham University, in a statement. “This ability has been suggested to be at the heart of human nature.”
The team on the new study looked at 1,242 natural play (above) and grooming (below) interactions between captive chimpanzees and, separately, captive bonobos. They found that the apes would regularly make eye contact alongside exhibiting other communicative signals when beginning and ending an interaction with another ape. They believe these signals to represent the kind of entry and exit phases practiced among humans when beginning and ending a joint commitment.
There were interesting differences between the two ape species, too. Bonobos performed hello and goodbye gestures in the form of touching, holding hands, butting heads, and gazing prior to playing 90 percent of the time, compared to 69 percent for chimps. They also performed them more often in exit phases, with bonobos and chimps scoring 92 percent and 86 percent, respectively.
Furthermore, compared to chimps, bonobos’ phases appeared to be influenced by their relationship with the specific individual which, the researchers say, could mean that these apes might reflect signals in a way that could be compared to “face management” in humans, a theory which explores how we may alter our expression to smooth out social interactions. “When you’re interacting with a good friend, you’re less likely to put in a lot of effort in communicating politely,” Heesen said.
If true, it could mean that our last common ancestor shares the trait of joint commitment, meaning that it evolved before we did, though further investigation is needed to know 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,” concluded Heesen. “Whether this type of communication is present in other species will also be interesting to study in the future.”