In 2022, world-renowned primatologist addressed the complex topics of gender identity and sexuality in the animal kingdom, most notably in his book, Different: Gender Through the Eyes of a Primatologist . His work explores how primates like chimpanzees and bonobos exhibit behaviors that challenge traditional human concepts of a rigid binary for sex and gender. Gender Diversity and Trans-like Behavior
De Waal argues that while biological sex is largely binary, "gender"—which he defines as the cultural and social expression of sex—exists among primates as well. He highlights that primate groups naturally produce and tolerate individuals who do not fit typical male or female molds: most notably in his book