How'd we get so choosy about friendships late in life? Ask the chimps

When humans age, we tend to favor small circles of meaningful, already established friendships rather than seeking new ones. People are also more likely to lean toward positive relationships rather than those that bring tension or conflict. No new friends, and no drama.

Three male chimps groom together in a chain. Likizo grooms Big Brown, who grooms Lanjo. Photo: John Lower

These behaviors were thought to be unique to humans, but it turns out that chimpanzees, some of our closest living relatives, have these traits, too. That information can help scientists gain a better picture of what healthy aging should look like, and what triggers this social change.

There is a pressing need to understand the biology of aging, these scientists say, especially with an increasing human life span.

The study draws on 78,000 hours of observations made between 1995 and 2016. Researchers looked at the social interactions of 21 male chimpanzees between the ages of 15 and 58 in Uganda's Kibale National Park.

The findings show what is believed to be the first evidence of nonhuman animals actively selecting whom they socialize with as they age.

The researchers looked only at male chimpanzees -- males show stronger social bonds and have more frequent social interactions than do females.

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

The older chimpanzees, for instance, preferred spending more time with -- and grooming -- chimps they had developed mutual friendships with over the years, while younger chimps had more one-sided relationships where grooming wasn't always returned.

Older males were also likely to spend time interacting with their aging friends. And, like older humans looking for some peace and quiet, the chimpanzees also showed a shift from negative interactions to positive ones as they reached their twilight years. (National Science Foundation)

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