Although gender expression has flourished in the wake of feminist, queer, and trans interventions, our society as a whole still claims the primacy of “biological sex.” From the fetishization of trans peoples’ genitals and tales of “transition” (Carmen Carrera and Laverne Cox took down Katie Couric on this point), to constant mis-gendering in mainstream media (as with the treatment of Janet Mock and Chelsea Manning), the policing of trans individuals makes evident a continuing reliance on “biological sex” as the ultimate determinant of identity.

In Sex Itself: The Search for Male and Female in the Human Genome (University of Chicago Press, $45), Sarah S. Richardson examines the biological grounding of sex at its apparent ...