Review - Evolution's Rainbow
Diversity, Gender, and Sexuality in Nature and People
by Joan Roughgarden
University of California Press, 2004
Review by George Williamson, Ph.D.
Jul 13th 2004 (Volume 8, Issue 29)

Evolution's Rainbow is the first work for a popular audience by the distinguished Stanford biologist, Joan Roughgarden, and as such, perhaps marks an auspicious beginning.  The book reads well, and does an enviable job of covering technical material with facility and grace, not to mention humor.  But it has a personal edge as well: it is devoted to redressing our cultural failure to do justice to the diversity of sexual and gender expression in both the natural and human worlds, and Roughgarden happens to be a male-to-female transsexual.  Her personal interest and insight are pervasive, but polemics are strictly kept to a minimum.  Evolution's Rainbow offers a serious critical perspective on various theories that tend to minimize, exclude or pathologize sex and gender diversity.  Suitably, a diversity of information from the sciences is presented, with many fascinating illustrations of animal and human forms rarely seen in televised nature programming.

Though her critique is wide-ranging, Roughgarden's targets are easily named.   At broadest, she indicts a number of academic disciplines ranging from biology and evolutionary science to anthropology and theology, for the suppression of diversity.  An example of this suppression is the long-standing difficulty in getting information on animal homosexuality into the academic record.  As she documents, such information has been ignored or 'explained away' to the present day.  Of course, the charge of discrimination has often been leveled at Western culture's concept of sex and gender, and neither this concept nor its critique are any longer unfamiliar.  But Roughgarden's case is refreshing in its particularity and detail.  Conventional assumptions regarding the fixity and generality of gendered behaviors and roles, of their binate structure, of mating strategies, and even of body plan of the sexes very quickly begin to appear naive when faced with examples of fish that change gender and sex in the course of a life, all-female lizard species that clone themselves yet still have (lesbian?) sex, bird couples with 'open' relationships, primate species whose members are completely bisexual, and fish whose reproductive strategy involves the collaboration of three distinct genders.  But such data are routinely discounted through the assumed normality of a male/female gender binary.  Much as the cultural projection of normative gender roles tends to push divergent sexual expression to the margins of the everyday social world, so has it tended to promote the exclusion of conflicting data in biology, or the pathologizing of expression in medicine and psychology.  And this must have consequences, for such omissions invalidate the theorization of sexuality and gender, for example, in evolutionary theory.  How could one accurately account for the evolution of sexuality, having left aside the data on same-sex relations or tri-gendered families?               

Indeed, one of Roughgarden's specific targets is the theory of sexual selection.  Darwin imported into evolutionary theory a sex role binary that seems rather transparently to be more at home in his own Victorian middle-class world than in the world of his data.  Sexual selection theory posits as universal (or near universal) a sexually competitive male bearing outward signs of his possession of good genes (beauty, size, power) paired with a comparatively passive female who is sexually coy, but discerning in the interest of acquiring the best possible genes for her offspring.  Ex hypothesi, the purpose of sex is simply the transfer of sperm between suitable mates.  This template, which putatively explains differential male and female appearance, tendencies and patterns of behavior, is treated as a normative model for sexual reproduction.  But taking shots at nineteenth century theory may be rather easy, so Roughgarden turns her attention to contemporary sexual selection theory and finds it little better, introducing into the picture mistakes even Darwin didn't make, such as attributing supposedly greater male promiscuity to the supposed cheaper cost of producing sperm.  A special target here is evolutionary psychology, lately seen rationalizing rape on empirically false or theoretically dubious suppositions.

Roughgarden's complaint against sexual selection theory is that the diversity in the data tends to disappear behind this normative binary.  Darwin was aware of considerably greater diversity in the natural world than his theory seems to allow, yet dismissed it as "rare exceptions" to the general rule.  By contrast, the detail presented in Evolution's Rainbow indicates sexual selection theory is wrong about nearly everything.  Body plan does not conform to a rigid sex binary: some species do not have a visible sex distinction, and in species that change sex, sex isn't even fixed within a body.  Nor does gender conform to a binary in every case, and nor does it mean the same thing in every species.  Also, sex roles in courtship, mating and parenting seem to be reversible.  And this is not even to mention homosexuality, with which sexual selection theory can scarcely cope at all.

Roughgarden recommends eliminating sexual selection from evolutionary theory, and instead proposes her own view, social selection.  Courtship, she argues, is not about discerning a male's genetic quality but rather about determining his likelihood of investing in parental care for offspring.  Sex is not merely about sperm transfer, but rather about forming bonds within animal societies and negotiating for access to resources necessary to reproduce.  Further, the evidence adduced suggests this negotiation goes on in within-sex relationships as much as in between-sex relationships, such as in a group of females who share parenting among themselves.  So the picture of sex that emerges is that mating is about building social relationships first, and only secondarily about passing on genes.  This explains why much more sex than reproduction happens, including much non-reproductive sex, and also allows a clear account of homosexual sex.  The real beauty is that it does not require an explanation for homosexuality different from that for heterosexuality: both are about forming social relationships and negotiating access to resources.  Differences in the prevalence of homosexuality in different animal societies can be attributed to differences in the relationships (between-sex, within-sex) which organize and distribute resources within those societies.  Indeed, the prominent secondary sex characteristics, which at face value appear to be the basis of mate choice (the peacock's tail, the predator's size), may not be intended for the opposite sex at all.  Roughgarden introduces the notions of a social-inclusionary trait, the possession of which gives an animal inclusion within a group and thereby, access to reproductive opportunities.  An example of this might be the penis of the female spotted hyena: used to signal in relation to other females, it enables group membership, without which a hyena may not get the chance to reproduce.  Roughgarden suggests that social-inclusionary traits may be able to account for most or all of the traits usually thought of as guiding mate choice under sexual selection theory.

A couple more of Roughgarden's targets are worth mentioning.  Psychology and medicine have had considerable influence in forming our ideas of normality in behavior and body morphology, and thus in legitimating differential treatment of those who deviate from the norm.  Homosexuality, for instance, until recently was listed as a mental disorder in psychiatry; transexuality still is.  There still remain groups offering to treat and cure homosexuality.  Children born with atypical genitals (penis too small, clitoris too large, some of both sexes) are often subjected to reconstructive surgery to correct their 'ambiguity'.  Evidently, diversity is 'not good' in the eyes of the medical and psychological establishment.  Having documented some of the disastrous consequences of these procedures, Roughgarden raises the reasonable question, "who really needs a cure?"  She challenges some of the dubious bases provided for labeling these traits as diseases or genetic defects, and concludes that our tendency to pathologize difference is really what needs to be cured.

To this end, the book closes with some policy recommendations, ranging from the practical to the symbolic.  Medical and psychiatric professionals, she suggests, would benefit from being made familiar, through education, with the true range of diversity.  Such curriculum change may be regarded as innocent or benign, but more resistance will likely be provoked by further steps such as FDA regulation of therapy methods and of the official classification of diseases, apparently a proposal for external oversight of psychiatry and medicine.  Finally, she suggests a monument to diversity be erected on the West Coast, to match the Statue of Liberty on the East Coast.

There is much more in the wealth of detail Evolution's Rainbow provides which cannot be adequately covered here.  Most neglected is the entire third part on diversity in various cultures.  Having examined diversity in the natural and human worlds in the first two parts of her book, Roughgarden turns her attention to such sources as the Old Testament, reports of New World explorers and contemporary Indian culture to reveal the absence of a credible single norm of behavior.  The message of the book is clear and cogently reasoned: diversity, whether in the natural or human world, is a good thing and deserves our respect.

© 2004 George Williamson

George Williamson, Ph.D., Department of Philosophy, Lakehead University, Thunder Bay, Ontario, Canada