Rebecca Jordan-Young’s Brain Storm is the first comprehensive critical analysis of studies that purport to show a link between testosterone exposure in the womb and the so-called “sexual brain” (meaning everything from the idea that there is a male versus female brain, to the idea that sexual orientation is caused by early hormone exposures). As Jordan-Young puts it on her website, to say she found this theory to be unsupported by evidence is “a bit of an understatement.”
Jordan-Young’s most recent work takes aim at the methods of “gender verification” employed in the governance of elite female athletic competition. Various athletic associations have been scrambling to set guidelines (both legal and scientific) for determining exactly who should be qualified to compete as a woman. The International Olympic Committee, arguably the sporting world’s most influential rule-setter, has a new policy that is expected to ban women with naturally high testosterone levels, on the grounds that elevated levels of the hormone give them an unfair advantage.
As Jordan-Young and Katrina Karkazis explain, this policy is neither fair nor rational:
(W)hen it comes to sex, sports authorities should acknowledge that while science can offer evidence, it cannot dictate what evidence we should use. Scientifically, there is no clear or objective way to draw a bright line between male and female.
Testosterone is one of the most slippery markers that sports authorities have come up with yet. Yes, average testosterone levels are markedly different for men and women. But levels vary widely depending on time of day, time of life, social status and—crucially—one’s history of athletic training. Moreover, cellular responses range so widely that testosterone level alone is meaningless.
Jordan-Young and Karkazis argue that if what we’re actually seeking is clarity then “it’s time to stop pawning this fundamentally social question off onto scientists.” And they go on to note that sex testing of female athletes will always be discriminatory, in that men will most likely never be subjected to similar verification. With competitive fairness underwriting these regulations, there’s little concern that a scientifically unqualified male (whatever that means) would have an advantage over scientifically verifiable ones (again, whatever that means).
And so these policies are ostensibly rooted in the notion that female athletes must be “protected” from competition against men. “Protection has been the cloak that covers all manner of sex discrimination,” write Jordan-Young and Karkazis, “and it is seldom, if ever, the best way to advance equality.”
In perhaps the most damning point against policies based on testosterone levels, Jordan-Young and Karkazis explain that there’s no valid reason to equate higher testosterone with enhanced performance. Not only is testosterone not “the master molecule of athleticism,” but the performances of women who have been found in violation of policies such as that being considered by the IOC have not been out of line with those of other elite female athletes.
Interestingly, just last month Sports Illustrated ran an article on “The Transgender Athlete,” investigating “what happens to athletes whose physiology doesn’t match their gender identity” when they enter the sexually segregated realm of sport. “Against whom do they compete? What obstacles do they face? And how are they being treated by sports' governing bodies?”
There’s obvious overlap here with the issue of sporting organizations attempting to scientifically determine eligibility, and governing bodies demonstrate a reliance on hormones as the determining factor in each case. Further, policies in each instance seem clearly driven by the apparently threatening specter of “biological men” infiltrating competition meant for women.
As Pablo S. Torre and David Epstein explain in their SI piece, the IOC ruled in 2004 that “any trans athlete who wants to compete against those not of their birth sex must undergo sex reassignment surgery and then two years of hormone therapy—either testosterone supplementation (to go from female to male) or testosterone suppression (to go from male to female).” The NCAA, which oversees collegiate athletics in the United States, last year announced a decision against requiring surgery, though it requires trans female athletes to undergo at least a year of testosterone suppression before they can compete against women. The NCAA allows trans males to receive medical exemptions to take testosterone under a doctor's supervision, but doing so renders them ineligible to compete on women’s teams.
And so, as the article documents, there are trans male student athletes who are in the position of postponing hormone therapy in order to preserve their eligibility to compete against women. Delaying a more full embrace of one aspect of their identity, in other words, so as not to jeopardize the institutional blessing of another. And all at the mercy of the pseudo-science of hormones.
Jordan-Young and Karkazis acknowledge the rationale for sex segregation in some sports at some levels, but ultimately argue in favor of policies that treat sex segregation as just one means to achieve fairness, rather than its embodiment.

