How different are men and women? Do they differ naturally or artificially? Do we find the same differences in our fellow primates? Do apes learn sex roles, too, or is “gender” uniquely human?

In Different, primatologist Frans de Waal draws on studies of both human and animal behavior to argue that a distinction between (cultural) gender and (biological) sex is useful to draw attention to the eternal interplay between nature and nurture. But even though gender goes beyond sex, biology is always part of the equation. Some human gender differences are universal and resemble those found in the apes.

Different provides a thought-provoking review of the long-running debate about the origins of sex and gender. De Waal peppers his discussion with details from his own life—a Dutch childhood in a family of six boys and decades of academic turf wars over outdated scientific theories. He also discusses sexual orientation, gender identity, and the limitations of a strict binary. Nature produces more variability than most human societies are prepared to recognize, he says, and primate groups often include (and tolerate) exceptional individuals.