Some Apes Say 'Hello' and 'Goodbye' Much Like Humans
Apes like chimps and bonobos use signals to start and end interactions much like humans do, according to new research published in iScience.
They exchange looks and often sign to each other — by touching, holding a hand, or extending an arm (or foot) to show they want to join or leave an activity.
Researchers studied more than 1,200 interactions among 50 chimps and bonobos in US and European zoos.
They discovered that bonobos exchanged "hello" signals 90% of the time, and chimps 69% of the time. "Goodbye" signals were more frequent — 92% of the time for bonobos and 86% for chimps. "Hello" interactions took an average of 12-13 seconds, while "goodbyes" took 14-17 seconds.
The researchers say these actions demonstrate an ability to agree to a "joint commitment" with others, in which they experience shared obligation while carrying out an activity, and also an ability to agree when the commitment has been fulfilled.
Raphaela Heesen, one of the study authors, said the ability to signal intentions and work on a common goal has allowed humans to achieve things in groups that we couldn't have achieved as individuals.
"We were able to launch rockets and land on the moon because we have the ability to share our intentions," she said.
Since bonobos and chimps are our closest relatives, their behavior could help scientists understand how ours developed, wrote the researchers.
Factors including how close the apes were to each other socially or who had more power were also studied.
Rank didn't seem to make much difference to greeting and leaving behavior for either species. However, if bonobos had a close social bond, their "hellos" and "goodbyes" were shorter.
"When you're interacting with a good friend, you're less likely to put in a lot of effort in communicating politely," Heesen said.
The researchers say more work needs to be done to understand how apes coordinate greeting and leaving behavior, especially in the wild. Joint commitment behavior may also be found in other species, they said.
