Ankur Desai

And we spent many years documenting the cooperative behavior of the male chimpanzees in this group.

And with that cooperation, they were able to dominate their neighbors, they expanded their territory as a result, they gained more food, and they gained fitness or reproductive benefits.

And the group increased even more in size.

So it sounds like things were going swimmingly and then there was a moment and then violence broke out.

Exactly.

Things were going swimmingly.

quite well for them, and that's one of the things that makes this study hard for me to understand and come to grips with.

They were actually benefiting in so many ways by living in this large group, but they probably reached a breaking point where, in a sense, they became victims of their own success.

The group grew so large that they couldn't hold together anymore.

Feeding competition intensified, reproductive competition among the males intensified, and a few males died just before hostilities broke out in 2015.

And as a result of that, there could have been changes in social dynamics elsewhere.

leading to hostilities that weren't there before.

There was a change in the alpha male right around the same time.

That often leads to increased levels of aggression.

There was this combination of factors that came together that led to the split.

And can we learn anything about our own human capacity for violence or conflicts from times when it seems that it's peaceful and then suddenly things erupt?

Can we learn anything at all?

I've studied chimpanzees now for a very long time, and if there's one thing I've come to learn is not how similar they are to us, but that they're different.

We've known for a very long time that chimpanzees will kill and attack their neighbors.

The surprising finding reported in this paper is that they will do so even when those neighbors are former friends and allies.