In the human world, as in the animal world, representatives of different sexes behave differently. World-renowned primatologist Frans de Waal has been observing monkeys both in the wild and in research centers for more than forty years. On the pages of the book, he asks questions that underlie any discussion about gender identity. By drawing analogies between animals and people, the scientist questions many social stereotypes regarding men and women. In particular, can male aggression or dominance always be explained by biology? Or is it more imposed by society? The author contrasts the cruelty of chimpanzees with the peacefulness of bonobos, and the leadership of the males of one species of monkeys with the matriarchy of another. Based on scientific data, de Waal argues that in order to understand the nature that determines the difference between masculinity and femininity, one must see the diversity of qualities of primates and other mammals, without giving preference to any gender. We are different to live together.