For 25 years, researchers have studied the chimpanzees in the Kibale National Park in Uganda.
They have looked at what the chimpanzees' lives look like and, among other things, how they age.
The researchers have followed them from morning to evening every day and have written down everything the chimpanzees do during the day.
Researchers Zarin Machanda and Alexandra Roseti have now examined the chimpanzees' friendships.
Better friends
What the study could show was that the older chimpanzees had very strong ties to their friends.
They were not as social anymore, but when they hung out, they really invested in the relationship.
The younger chimpanzees seemed to look up to the older ones' close friendships, as if they themselves wanted them.
But they did not know how to create them.
- From our point of view, it is very interesting that the older chimpanzees are still popular even though they have lost dominant status in the group.
This is something we have not seen before, says Zarin Machanda, professor of primatology.
Similar to us humans
Just like us humans, the chimpanzees themselves choose who they want to hang out with.
We humans like to keep our old friends and do not like to get new ones.
- I was quite hard on my mother when she moved to a new city did not go out and make new friends.
She said, I do not need new friends, I have friends.
And what we have seen now is a similar pattern in chimpanzees.
They are not as social as they get older but they take care of the relationships they have, says Zarin Machanda.
The older chimpanzees also seemed to be more content with life and more positive than the younger ones.
Something that researchers think may have to do with the fact that they have so many friends.
- It shows the same changes that can be seen in us humans as we age and may have evolutionary roots, says Alexandra Rosati, professor of anthropology and psychology.
The study is published in Science.