I have often noticed how primate groups in their entirety enter a similar mood. All of a sudden, all of them are playful, hopping around. Or all of them are grumpy. Or all of them are sleepy and settle down. In such cases, the mood contagion serves the function of synchronizing activities.

If we look straight and deep into a chimpanzee's eyes, an intelligent self-assured personality looks back at us. If they are animals, what must we be?

I was raised Catholic. Not just a little bit Catholic, like my wife, Catherine. When she was young, many Catholics in France already barely went to church, except for the big three: baptism, marriage, and funeral. And only the middle one was by choice.

Humanity is actually much more cooperative and empathic than [it's] given credit for.

If both parties have a stake in the other, the chances of them killing each other are going to be reduced.

The evolutionary struggle for survival is really a self-serving series of blows and stabs, and yet it can lead to extremely social animals like dolphins, wolves or, for that matter, primates.

Studies of reconciliation in primates have demonstrated that if the relationship value increases between two parties they are more willing to make peace.