I've argued that many of what philosophers call moral sentiments can be seen in other species. In chimpanzees and other animals, 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.

We are by far the most contradictory of all primates. An animal with this much internal conflict has never lived on this earth.

If you are a cooperative animal you need to watch what you get. If you, or even a whole community, invest in something but then a few individuals receive a much larger return, it's not a good arrangement. If it happens consistently, it's time to look for an arrangement that is more beneficial. That's why we're so sensitive to how rewards are being divided.

Male chimpanzees have an extraordinarily strong drive for dominance. They're constantly jockeying for position.

Most men probably wouldn't want to live the lives of bonobos. They're constantly clinging to their mothers' apron strings. They lack the ability to make decisions about their own fates, something that we and male chimpanzees practically consider our birthright.

To endow animals with human emotions has long been a scientific taboo. But if we do not, we risk missing something fundamental, about both animals and us.

The hamadryas baboon is a harem holder where one male mates with multiple females.