Fausto-Sterling is a biologist who challenges various experiments meant to prove the biological bases of sexual difference. The first chapter is a brief introduction describing the interdependence of modern social structure and biology. Chapter Two is called "A Question of Genius: Are Men Really Smarter Than Women?" She is partly concerned here with arguments that women are simply less intelligent than men. More interestingly, she takes on scientists who claim that women have a different sort of intelligence than men (more verbal than visual or spatial). Such claims, argues Fausto-Sterling, simply provide a rationale for sexism in education and employment. Fausto-Sterling questions both the techniques used in the experiments meant to prove these differences and the scientists' objectivity. Chapter Three, "Of Genes and Gender," similarly critiques theories that suggest humans are totally controlled by genetic information. Particularly, she argues that the binary genetic sex model under which biology works is not nearly as obvious or secure as it seems. The author also points out that studies of "sexual development" are almost always about men. This chapter contains discussions of medical views of menstruation and menopause. The author ridicules positions that see menstruation as a disease or sick-time. Chapter Four moves the discussion to testosterone, arguing against the equation of testosterone with aggressivity and natural superiority. Chapter Six takes on socio-biology.