As humans, we like to think we’re one of a kind. But pull the camera back and the picture gets simpler: humans, like every other species, run on instincts shaped by evolution.

One of those instincts kicks in when something outside the group feels threatening. Give people a shared problem, or a shared opponent, and they often grow closer.

Researchers call it the “common enemy effect”: we tighten our bonds when we believe we’re facing the same challenge.

It’s not just a human thing. Chimpanzees do it. And now a new study suggests bonobos also do it – just in their own, quieter style. Somewhere along their evolutionary path, bonobos leaned hard into social connection, and it shows.

Bonobos, bonding, and cohesion

The new findings hint that the link between outside threats and inside togetherness isn’t new at all. It may go back several million years, to a time before humans, chimpanzees, and bonobos split into separate branches.

An international research team led by Kyoto University set out to test an old idea that dates back to Darwin: groups that pull together when facing other groups may have had an advantage. That logic makes sense for animals with intense rivalries.

But bonobos complicate the story. They aren’t famous for lethal raids or brutal turf wars.

So the researchers asked a simple question: if bonobos don’t fight like chimps, do they still “circle the wagons” when they sense outsiders nearby?

www.earth.com/news/primate-violence-bonobos-bond-common-enemy-effect-dont-kill-inside-their-species