When World Athletics (WA) announced the return of systemic sex testing leading up to the 2025 World Championships in Tokyo, it was framed it as a necessary measure to protect the female category.
But for Marcus Mazzucco, an adjunct lecturer at the Faculty of Kinesiology and Physical Education, the policy shift looks less like protection and more like a return to a darker chapter in sport history.
In response, Mazzucco co-authored an article called Sex Testing in Women’s Sport: Historical Harms, Contemporary Risks, and World Athletics’ 2025 Policy Shift. The research takes a critical look at WA’s decision to reintroduce mandatory genetic screening for female athletes—a practice that was formally abandoned by the organization in 1992.
In the lead-up to Tokyo, WA reported that over 95 per cent of female athletes had completed a mandatory, once-in-a-lifetime screening for the Sex-determining Region Y (SRY) gene.
While the policy aims to create a clear-cut method for eligibility, Mazzucco’s paper argues that the science is not so black and white.
“Attempting to simplify the complex biology of sex to a single element—like the SRY gene—is often insufficient,” says Mazzucco.
“Sex is a multidimensional biological construct, and the SRY gene test has limitations that the International Olympic Committee acknowledged when it ended compulsory testing for the gene in 1999.”
The new regulations also signal a major shift in how WA categorizes athletes. The regulations merge eligibility standards for women with variations of sex characteristics and transgender women into one set of rules, signaling that WA is prioritizing biological sex over gender in its criteria.
In their study, Mazzucco and his co-authors analyze this shift in light of the history of sex testing in sport—a history fraught with substantial objections from medical, scientific and ethical bodies.
“By reviving genetic sex testing, the WA is recycling old models that were discarded for good reason. Beyond the historical and scientific concerns, these regulations are vulnerable to legal challenge under anti-discrimination, data protection and genetic testing laws,” says Mazzucco.
You can read the full paper in the journal Frontiers.