The International Olympic Committee announced a new policy on March 26, 2026, for women’s competitions: Every athlete must be tested for a gene called SRY, usually found on the Y chromosome. Males typically have a Y chromosome and females typically don’t, so the IOC says this requirement will exclude “biological males.” This announcement comes as planning for the 2028 Summer Olympics, hosted in Los Angeles, is underway.
But the IOC statement hides the complexity of biological sex and continues the organization’s century of what the record shows is inconsistent and biologically unsound sports policies.
I’m a biology professor and author of an upcoming book, “The Binary Delusion: How Biology Defies the Myth of Two Sexes.” While the impetus for the new policy seems to be exclusion of transgender women from women’s athletics, it will more likely exclude and draw unwelcome publicity to many more women who are not transgender.
Few elite athletes are transgender
Transgender people have faced mounting legal and political attacks in recent years.
President Donald Trump issued an executive order on Jan. 20, 2025, asserting that biological sex is simple and binary – that everyone is unambiguously female or male – and another executive order precluding “males” from women’s competitions.
At least 29 U.S. states have excluded transgender girls and women from girl’s and women’s athletic competitions. These laws are built on the idea that men on average are superior to women in many sports, so women need to be protected from unfair competition.
Numerous state bills have aimed to ban transgender athletes from participating in sports.
Oliver Contreras/AFP via Getty Images
But elite transgender athletes are rare. In a 2024 hearing before the U.S. Senate, the president of the NCAA testified that of the 510,000 athletes in U.S. colleges at that time, he was aware of fewer than 10 transgender athletes – less than 0.002%.
Only one known transgender woman has ever participated in an Olympic women’s competition since the committee allowed women to compete in the Games beginning in 1900: Laurel Hubbard, a weightlifter who competed for New Zealand in 2021 but did not medal.
The rarity of transgender athletes in elite competition suggests their exclusion is a solution in search of a problem.
Biological sex is complicated
The genetic test the IOC is requiring is more likely to identify intersex women.
Intersex people have a combination of typically female and typically male biological sex traits. These include sex chromosomes, internal and external reproductive anatomy, sex hormones and hormone receptors.
There are many variations of intersex traits, but three may be the most relevant for women’s athletic competitions: androgen insensitivity, 5-alpha-reductase deficiency and genetic mosaicism.
People with androgen insensitivity don’t respond as much to androgens like…
