It’s not just us – older chimpanzees get fussy about their friends, too
You used to be my best primate, Dave
AS HUMANS enter middle age, they become more selective about their social circle. And it turns out that chimpanzees are exactly the same.
Researchers monitored 21 male chimpanzees for more than 20 years. The older animals, in a group aged from 15 to 58, had smaller circles of friends and were more likely to focus on existing close relationships. Younger chimps persisted in trying to befriend other males – sitting next to animals which rarely chose to sit next to them.
But the older animals decided that was too much effort. They had more ‘mutual’ friends, who chose to sit next to them too, and tended to also engage in more grooming.
Dr Alexandra Rosati, one of the authors of t he University of Michigan study, said: ‘The really cool thing is that we found that chimpanzees are showing these patterns that mirror those of humans... even though they do not have the same sense of future time. As chimpanzees get older, they also focus on their important, positive relationships and actually become more popular in the group.’
Chimpanzees, which live for up to 60 years in the wild, reach adulthood at the age of 15. Although males spend less than 1% of their time alone, older chimps were f ound to be more solitary. It appeared they valued loyal friends more, with 40-year- old chimps having three friends on average that they wanted to sit next to and wanted to sit next to them.
This fell to one loyal friend on average for adult chimpanzees aged 15, the study in Uganda’s Kibale National Park found.
People are believed to revert to close friends and cut ties with less loyal acquaintances as they become more aware of their own mortality.
It is not clear why chimps, which do not know they will die, do the same thing. It may be because they are older and less healthy so could benefit more from help from reliable friends. The research was published in the journal Science.