In Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People, Joan Roughgarden, an evolutionary biologist, translates difficult concepts from biology, medicine, genetics, theology, and the social sciences into the vernacular for a wide audience. Rainbow means diversity, and the book deals with diversity in three areas: diversity in reproduction and family organization among animals; diversity in human biology and the cooperative interaction of genes and hormones in development; and sexual and gender diversity across cultures and history. This is a scientific book—study after study is critically analyzed and well-referenced in fifty pages of chapter notes—but Roughgarden, a transgendered female, has a social agenda. By refuting Darwin’s sexual selection theory and affirming biodiversity, she seeks to end notions of male superiority and discrimination against people of diverse gender and sexual orientations.
Darwin claimed that, in mating, males have greater passions than females, compete for the female’s attention, and the female’s choice of the stronger (or more beautiful) male improves the species by weeding out weaker candidates. Roughgarden cites numerous studies of species where the less attractive or weaker animal is accepted by the female, and where cooperation, not struggle, determines the outcome. Her formidable review of diversity in animal sexual behavior also challenges the assumption that the bimodal (male and female) model of sexuality is universal or even desirable. She asserts that these studies have been ignored by scientists because their findings do not support Darwin’s theory.
Roughgarden’s discussion of human biology and development stresses that people cannot be divided into two categories—normal and abnormal, gay and straight, healthy and diseased—but that in everything, including the development of sexual orientation, there is diversity in every detail. A survey of sexuality and gender expression in different cultures, including the United States, focuses on the need to affirm diversity.