Imagine that we didn't know the chimpanzee, that all we knew were those bonobos who have sex all the time and are peaceful and female-dominated and t… - Frans de Waal

I've argued that many of what philosophers call moral sentiments can be seen in other species. In chimpanzees, gorillas, orangutans and humans, you see examples of sympathy, empathy, reciprocity, a willingness to follow social rules. Dogs are a good example of a species that have and obey social rules; that's why we like them so much, even though they're large carnivores.

I would say there are people in this world who like hierarchies, they like to keep people in their place, they like law enforcement, and they probably have a lot in common, let's say, with the chimpanzee. And then you have other people in this world who root for the underdog, they give to the poor, they feel the need to be good, and they maybe have more of this kinder bonobo side to them. Our societies are constructed around the interface between those two, so we need both actually.

At the time, I was interested in reconciliation after fights, and I wanted to know how bonobos did it compared to chimpanzees. Very soon I discovered that they were much more sexual in everything they did, and that interested me — not so much for the sex part, even though that became a very hot topic, the peacemaking-through-sex thing — but much more how they have such a peaceful society, because they are much less violent than chimpanzees.