Joan Roughgarden is a professor of biological sciences at Stanford Univeristy -- and a woman who was once a man. As such, she has a keen interest in sexual variation, a subject she addresses in Evolution's Rainbow: Diversity, Gender, and Sexuality in Nature and People (Univ. of California, $27.50). One of the many surprising scientific findings she reports is that exclusively straight male bighorn sheep -- those who do not engage in sex with other males -- are, from many points of view, "effeminate." "These males are identical in appearance to other males," she writes, "but behave quite differently. They differ from 'normal males' by living with the ewes rather than joining all-male groups. These males do not dominate females, are less aggressive overall, and adopt a crouched, female urination posture." Meanwhile, most male bighorn sheep are busy having intercourse with both females and other males. "This case," as Roughgarden adds, "turns the meanings of normal and aberrant upside down."

Toward the end of the book, Roughgarden engages in some Biblical interpretation, focusing on the passages that are "cited . . . against gay and lesbian people." She argues, for example, that Paul's criticism of homosexuality in his letter to the Romans can actually support a pro-gay reading. "The sense of Paul's letter," she writes, "is that if someone who has been worshipping God gives this up to follow other deities, their behavior will become unnatural for them -- they will start behaving out of character. . . . For someone who is primarily gay, the opposite is unnatural. For people who are gay to force themselves into heterosexual sex may be unnatural for them, and unfair to their partner, too."

-- Dennis Drabelle