The problem with defining “biological females"

One week ago today, on June 30, the Supreme Court issued a ruling that addressed two cases, West Virginia v. B.P.J. and Little v. Hecox, about whether states may ban transgender athletes from participating in girls’ or women’s sports. The Supreme Court’s ruling is horribly misguided, as the history of athletic sex-testing programs shows.

updated version with corrections made on July 8!

The LGBTQ advocacy organization Lambda Legal succinctly explained the legal issues: “The two cases argue that the bans [on transgender girls or women participating in organized sports] violate the rights of two transgender female student-athletes under the Equal Protection Clause of the Fourteenth Amendment of the U.S. Constitution. In addition, West Virginia v. B.P.J. argues that the ban violates Title IX, the federal law prohibiting sex discrimination in educational programs. Federal courts have blocked enforcement of these bans in both lawsuits.”

In its recent ruling, the Supreme Court overturned those federal court decisions and upheld the state bans, as Scotusblog summarized—with emphasis added by me:

In his 29-page opinion, Justice Brett Kavanaugh wrote that “[c]onsistent with Title IX and the Equal Protection Clause, we hold that the States may maintain women’s and girls’ sports for biological females. They may determine eligibility for women’s and girls’ sports based on biological sex. The Constitution and Title IX do not require an overhaul of women’s and girls’ sports throughout America.”

Justice Sonia Sotomayor wrote a dissent joined by Justices Elena Kagan and Ketanji Brown Jackson.

In the majority opinion, Kavanaugh’s frequent references to “biological females” and “biological sex” suggest that he and other members of the court know very little about the biology of sex. The decision rests on the false assertion that there exists a clear sex binary with obvious medical understandings of what makes a person male or female. But that is not true. Intersex conditions are surprisingly common, androgen levels vary widely among adults assigned male and female, and bodies develop in all kinds of different ways.

If you’re unsure what I mean, then think about how you might define a “biological female.” What are the fundamental criteria? If you were the administrator of a sports league, how would you decide whether a particular person was a “biological” female? A strip search? Gynecological exam? Affidavit from a primary care physician? Blood test for hormone levels or chromosomes?

• Is it chromosomes? If having XX chromosomes is what makes a person a “biological female,” then what about someone with XO or other “mosaicism”” condition such as XXY? Is it the absence of the Y chromosome that makes a person female?

• Is it hormones? Then what about someone who is XX, has a vulva, and since puberty has shaved their face? Is there a particular threshold for testosterone that defines maleness? What about men with low testosterone or especially high estrogen — are they disqualified from participating in men’s sports?

• Is it a question of external genitalia? Then what about someone who is XY, has no testes, and has a vagina? (Not to mention: do Kavanaugh and the other supporters of these bans seriously think that K–12 coaches should be requiring children to undergo gynecological exams in a doctor’s office?)

• Which definition of “biological sex” would you, as a sports administrator, apply, and how would you justify your criteria?

The attempt to impose a rigid definition of “biological female” on the bodies of people who want to participate in athletic competitions or clubs turns out to have an incredibly complex and disturbing history—one that should give pause to anyone who thinks there is something common sense or benign about sex-testing athletes.

The Other Olympians: Fascism, Queerness, and the Making of Modern Sports (2024), a prize-winning book by Michael Waters, offers a riveting account of how and why the International Olympic Committee (IOC) and other athletic organizations decided to evaluate the “biological sex” of athletes competing in women’s events. Waters builds his narrative meticulously, beautifully capturing the stories of talented athletes who either questioned their own gender identity or faced rumors and doubts from others. Controversy surrounding women’s sports as a broader enterprise—whether any woman should ever compete in athletics—shaped much of the conversation about whether certain athletes might be “too masculine” to meet supervisory officials’ unstated definition of woman-ness. Some supporters of sex testing programs considered participation in sports masculinizing, as if playing a sport might turn a girl into a sort of unsexed creature.

These issues came to a head in 1936, when the Olympics opened in Berlin with Adolf Hitler’s approval in stadiums festooned with Nazi flags. After Helen Stephens, an American track-and-field star, set a new world record for the hundred meter dash, she almost immediately faced backlash from skeptical reporters and IOC officials who speculated that Stephens was not “really” female. The imprecision of the allegations is crucial. As Waters shows repeatedly, none of the people warning about individuals who were not “biologically female” in women’s sports ever explained what criteria they used to determine if a person was or was not female. Waters writes,

Exactly what the newspapers were accusing Helen Stephens of was never made clear. Were they claiming that Stephens was intersex? That she was born a cis man and was masquerading as a woman? That she was just too masculine? Perhaps it didn’t matter. (214)

Although the IOC did not yet have a sex testing policy or protocol, newspapers reported that Olympic officials had required Stephens to undergo some sort of “sex test.” Given that DNA testing wasn’t available at the time, most likely an Olympic physician performed a gynecological exam. According to these reports,

The officials…had expressed concern about Stephens’s biological sex soon after her arrival, and Nazi authorities had asked her to undergo a physical examination to verify her sex before the start of the Olympics… If [the report was] true, it would mark the first time that an athlete was sex tested at the Olympics. Concerns about masculine women had reached such a fever pitch that Nazi authorities had physically inspected the body of a top American sprinter to determine whether she looked, to them, like their understanding of a woman. (215–216; emphasis added by me)

Concerns about masculine women had reached such a fever pitch that Nazi authorities had physically inspected the body of a top American sprinter to determine whether she looked, to them, like their understanding of a woman. (Waters, 215–216)

The International Amateur Athletic Federation (IAAF), which oversees track and field events, was the first group to create a formal sex testing program. It did so just days after the 1936 summer games wrapped. The head of the IAAF, an American named Avery Brundage, was unapologetically cozy with the Nazis. He had worked to discredit a campaign to boycott the 1936 Olympics, insisting that the Nazis were not really discriminating against Jews, and he now argued that the men who oversaw track-and-field competitions must determine whether the athletes in women’s events were really women. The IAAF adopted a policy, for women’s events only, requiring an examination of any athlete’s sex if another athlete alleged that their competitor was not “really” a woman and thus allegedly won by an unfair advantage.

Importantly, Brundage had no interest in the success of women’s sports. He believed that participation in athletics de-feminized most women, which was not how he preferred them. Waters quotes Brundage as saying that running track made a woman’s “charms sink to something less than zero.” (233) (Waters notes pointedly that during the same years Brundage was insisting that amateur athletes adhere to a rigid moral code, he had an extra-marital affair that produced two children, whom he refused to acknowledge.)

By the late 1940s, the IAAF considered requiring all athletes who wanted to compete in the Olympics or the European championships to present “a recent medical certificate of sex.” A French member of the IAAF leadership stated that any “cases which appear doubtful” would trigger a “special examination” of the athlete’s body. Waters notes that neither this official nor any other high-ranking athletic organization officials who supported sex testing ever defined the categories of woman or female, nor did they explain what precise qualities made someone’s sex “doubtful.” (258) Some athletes left amateur sports entirely rather than undergo coerced, invasive gynecological exams. They may also have feared damaging social repercussions if the examiners concluded that their bodies were intersex.

By 1966, the IAAF required on-site sex testing:

These were crude physical exams during which doctors would strip down women and inspect their genitalia… The organization either ignored or did not care to understand, the reality that genitalia was not uniform across people and could not be cleaved into binary sex categories of “male” and “female.” (270)

Waters shows that sex testing policies never worked. After the IAAF decided to test chromosomes in 1967, “[the policy] backfired almost immediately… Poland’s Ewa Kłobukowska [a sprinter]…was removed from competition when a test found she ‘had one chromosome too many.’” She had, in other words, “a chromosome mosaic, that rare condition with no bearing on a person’s biological sex or athletic performance.” (273)

There is much more to this book, and I recommend it highly. For now, I’ll let Waters have the last word:

Sex testing, from the start, was never about an actual threat to women’s sports. It was always about the perception of a threat; the ambient sense of panic around femininity, masculinity, and gender transition; the feeling that something fundamental was shifting in the relationship between gender and sports and that the only way to stop it was to forcibly examine the bodies of anyone deemed suspect. It was policy rooted not in real harm, but in abstract fear. (225)