Roughgarden begins with a review of sex and gender in animals and plants, structured to challenge current theories of sexual selection. She then describes the development of the embryo, the psychology of sex and gender diversity, and the treatment of sexually diverse people in ancient and modern cultures. She ends with policy recommendations for modern American society. The book is held together by her demand that we rethink our attitudes toward human diversity. In the calculus of reproductive success, homosexuals who divert mating energy to nonreproductive partners have always posed a problem to evolutionary theory, and people who choose to be celibate or sterile even more so. On the book's first page, Roughgarden suggests, "When scientific theory says something's wrong with so many people, perhaps the theory is wrong, not the people."
She describes the rainbow of sexuality in other species: hermaphrodites, sex changers, homosexual matings (known from more than 300 vertebrate species), species with three or more "genders," pairs of male swans who fledge more young than male-female pairs, and trios of bluegill sunfish (in which big territorial males court smaller male partners as well as females, and then the threesome spawns together). Roughgarden discards the idea that all these animals are "deceived" by mimicry of the other sex or "cuckolded" by sneaks. Often, she argues, they are cooperating in a wider social context than the simple reproductive pair.
She proposes that the theory of sexual selection should be replaced by one of "social selection," in which all the bonds between members of a society are recognized--including mating relationships that promote kin selection in the widest sense rather than individual reproduction. I agree that far too much of sexual selection theory has concentrated on species that mate at a lek (what Roughgarden calls a male red-light district), where females choose between posturing males who give them nothing but genes. Fascination with showy, competitive males and coy females has continued from Darwin down to present-day popularizers.
However, biologists already study the trade-offs among strategies such as showiness, aggression, mate-guarding, parental investment, queuing for reproductive opportunities, and helping at the nest. If we consider homosexual behavior as a possible benefit, not a cost, we only extend what is in effect already a theory of social selection. We will still continue to see evolution as fundamentally about which genes make it into the next generation. Even Roughgarden does not go as far as the activist who asks, "Why is biology so hung up on reproduction? This does not reflect the reality of my life or what I see around me." I think we don't have to choose one version or the other. For a less emotive example, walking evolved to get from place to place. Although it matters immensely whether we prance, dance, swagger, swish, scoot, shamble, stumble, or march in step, we still move from X to Y.
Roughgarden's treatment of embryonic development emphasizes its complexity, but she comes out on the side of biological bases for much homosexual and transgendered behavior as well as physical intersexes. This view can provide a kind of freedom that would be denied by those who think such behavior is wholly learned--and therefore that it can be unlearned or "cured." (Of course, in a more tolerant society, learned behavior could also be granted such freedom.) If a bias toward minority sexual patterns does start with the genes, such patterns are far more frequent than could be continued if such genes were deleterious. Therefore, the conclusion must be that there is positive selection for some proportion of those genes in the population. Roughgarden raises the specter of genetic engineering being used to tamper with the genes supposed to underlie these behaviors, and she counsels how ill-advised it would be to let current prejudices interfere with processes that human evolution seems to have found beneficial.
The book moves on to narratives of lives of transsexual people, from ancient eunuchs to modern Indian hijras. Roughgarden notes that Jesus recognized multiple types of eunuchs: "there are eunuchs who have been so from birth, and there are eunuchs who have been made eunuchs by men, and there are eunuchs who have made themselves eunuchs for the sake of the kingdom of heaven" (Matthew 19:12, Revised Standard Version). In all cultures, a few males have made themselves eunuchs out of a wish to be women. Most of those who talk about it claim that they knew they were born into the wrong sex long before their own puberty. Similarly, in all cultures there are a few females who live and act as men, from Indonesian tomboi to Joan of Arc. Following the arguments of Leslie Feinberg, Roughgarden describes Joan of Arc as "a male-identified trans person" who chose to be burned alive rather than wear women's clothing--and who was so convincingly masculine that her executioners raked away the coals to display her naked body and remove people's doubts that she was a woman.
In the last chapter, Roughgarden summarizes her position:
I believe the rainbow always has more colors than society has categories, and that society is always trying to cram humanity's rainbow into the few categories it does have. Social scientists have the opposite perspective; they think diversity results from society producing difference among people who are biologically the same. I don't agree. The biology I know tells of endless variation, not of a few universals.She ends her text with an agenda, a list of what she believes transgendered people want. It includes the desires "to be cherished as a normal part of human diversity"; "to be treated with courtesy and dignity"; and "to be respected as people, not bodies."
How successful is Roughgarden in her ambition to revolutionize current biological theories of sexual selection, and to use revised theory to explain and embrace human sexual diversity? Oddly, I think she fails in the first quest yet succeeds in the second. As I noted above, what Darwinian theory needs is not so much radical revision as a simple expansion to take sexual diversity much more seriously. This more encompassing emphasis must address the high frequency and the biological bases of life choices that do not lead to personal reproduction as well as the malleability of both sex and gender among other species. Evolution's Rainbow makes it clear that such a change, even if not revolutionary, would illuminate aspects of long-term evolution. But even more important, Roughgarden's heartfelt account shows how much a changed agenda is needed in the contemporary culture where each of us lives our own short life.
