Transphobes love invoking biology to justify their unmitigated hatred of transgender people, and it doesn’t really matter much to them whether their science is correct. This shallow and vapid misinformation is often countered in online discourse by arguments with only slightly more depth; unfortunately, we’ve seen in recent years transgender people coopting intersex identity and using (unintentional) misinformation to combat these arguments. The science of sex and gender is complex.

Joan Roughgarden is well-positioned to write this book. Not only is she a Professor of Biological Sciences at Stanford, she is also a Christian and a transgender woman herself. Her previous works have sought to reconcile Christian theology with evolutionary biology, and her 2004 book, Evolution’s Rainbow, shows similar bravery in taking on the theory of sexual selection head-on. Her book was as polarizing when it was published as transgender rights are today: in 2005, the book won the Stonewall Book Award, while simultaneously receiving widespread criticism from the biology community, accusing her of pushing a personal agenda. Of course, nobody ever accuses cisgender people of pushing a personal agenda when they concoct theories rooted in heteronormativity. But I digress.

The book is split into three parts: first, she explores variations in sex and gender in the animal kingdom. This includes behavioral and physical traits, such as with the plainfin midshipman, a fish that has both large and small mature male, which each exhibit different behaviors during mating. The second part of the book discusses human sexual variation, including, of course, intersex conditions. Here, she presents an elaborate picture of the development of a human from conception to the first years of life, discussing in detail how genetic factors and hormones interact to determine sexual characteristics. The latter third deals with cultural variation in sexuality and gender, exploring, for instance, cultures where what we in the west might call butch lesbians actually present and are treated as something of a third gender entirely.

Each chapter is surprisingly readable and captivating, given the scientific content and difficult subject matter. I won’t summarize the book; I am not a biologist, and you can simply read it yourself. I will say that the book does have all the hallmarks of a text written in 2004. The use of “transgender_ed_” rather than “transgender” feels archaic today, and Roughgarden transitioned a generation before the trendy identity politics of the mid 2010’s set the foundation for the modern (or postmodern?) trans rights fight. Roughgarden’s somewhat inconsistent consideration of when a fetus is a human is clumsy enough with today’s abortion politics that it gives pause. And surely some of the scientific content can be updated.

Nevertheless, Roughgarden pulls no punches in taking on the weaknesses in sexual selection theory and the institutional forces that insist upon it. She eviscerates the field of psychology and presents a surprisingly modern lens elevating, but not glorifying, gender identities in non-western cultures. The book is heavy; at 400+ pages of biological and anthropological writing it’s a good swing to hit a TERF with, rhetorically. The arguments are more nuanced and well-researched than what you’ll find on Twitter, though it’s not like it matters. Transphobes aren’t bigots because of a misguided but earnest commitment to science and reason. Nevertheless, I think it’s an important read for anyone who does want to learn a bit more about sex and gender in nature and elsewhere. There are better books for learning about the social science aspect of transgender people in the world, but I’ve yet to find a book that goes into as much detail about the biological and biochemical elements as Evolution’s Rainbow does.

Evolution’s Rainbow
Joan Roughgarden
ISBN 9780520260122