It’s no secret that humans and apes share a host of traits, from the tribal communities we form to our irrepressible curiosity. We have a common ancestor, scientists tell us, so it’s natural that we act alike. But not all of these parallels are so appealing: the chimpanzee, for example, can be as vicious and manipulative as any human.

Yet there’s more to our shared primate heritage than just our violent streak. In Our Inner Ape, Frans de Waal, one of the world’s great primatologists and a renowned expert on social behavior in apes, presents the provocative idea that our noblest qualities—generosity, kindness, altruism—are as much a part of our nature as are our baser instincts. After all, we share them with another primate: the lesser-known bonobo. As genetically similar to man as the chimpanzee, the bonobo has a temperament and a lifestyle vastly different from those of its genetic cousin. Where chimps are aggressive, territorial, and hierarchical, bonobos are gentle, loving, and erotic (sex for bonobos is as much about pleasure and social bonding as it is about reproduction).