"It is true that the chimpanzee is dominance-oriented, violent, territorial. But it's also cooperative in many ways, and so that side is sometimes forgotten. The bonobo is sensual, sensitive, sexual, a peacemaker, but also can have a nasty side, and that's sometimes forgotten. So both species are sort of the ends of the spectrum, and we fall somewhere in between. Clearly, we have both of these sides in us, and that's why I sometimes call us "the bipolar apes.""