Credit: The Field Museum of Natural History in Chicago

No new friends and no drama.

When humans age, they tend to favor small circles of meaningful, already established friendships rather than seek new ones. People are also more likely to lean toward positive relationships rather than ones that bring tension or conflict. These behaviors were thought to be unique to humans but it turns out chimpanzees, one of our closest living relatives, have these traits, too. Understanding why can help scientists gain a better picture of what healthy aging should look like and what triggers this social change.

The work is described in the journal Science and is authored by a team of psychologists and primatologists, including current and former researchers from the Harvard Department of Human Evolutionary Biology.

The study draws on 78,000 hours of observations, made between 1995 and 2016, which looked at the social interactions of 21 male chimpanzees between the ages of 15 and 58 years old in the Kibale National Park in Uganda. It shows what’s believed to be the first evidence of nonhuman animals actively selecting who they socialize with during aging.

The researchers looked only at male chimpanzees because they show stronger social bonds and have more frequent social interactions than female chimps.

Analyzing a trove of data, the researchers saw that the chimpanzees displayed much of the same behavior aging humans exhibit.