How’d we get so picky about friendship late in life? Ask the chimps

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. The study shows what’s believed to be the first evidence of nonhuman animals actively selecting who they socialize with during aging.