Recent years have seen a concerted effort to overthrow the longstanding scientific consensus that “male” and “female” represent two real, discrete biological categories in humans. The Oxford philosopher Amia Srinivasan, for instance, rejects the notion that biological sex is “natural,” “pre-political,” or “objective,” claiming instead that it is “a cultural thing posing as a natural one.” UC–Riverside’s Gender and Sexualities Chair, Brandon Andrew Robinson, openly claims that we “should stop teaching that sex is biological” because we “assign meaning to certain things . . . because of dominant gender ideologies.” In this view, categorizing people as male or female is not only biologically incorrect but also harmful and oppressive.

Early attempts at debunking the two-sex model sought to expand the number of sexes beyond two. Consider Brown University professor Emerita Anne Fausto-Sterling, who claimed in the 1990s that the “two-party sexual system” in humans was “in defiance of nature,” and that there were instead “at least five sex categories, and perhaps even more.” However, the additional “sexes” she proposed simply corresponded to various intersex conditions, not new sexes akin to the functional reproductive roles of producing either sperm or ova that define males and females universally across all taxa.