At the end of March, the International Olympic Committee announced undoubtedly one of the most controversial decisions in its recent history: starting with the 2028 Los Angeles Olympic Games, no transgender athlete will be able to compete in the women’s category. But beyond the social and political debate that can be generated, we must also focus on the method chosen to determine this exclusion: a simple genetic analysis where a single gene is searched. And this is something highly discussed among science.
His discoverer. The gene in question, which will be analyzed in athletes who want to participate in the female category, will be SRYwhich is nothing more than the “Sex Determining Region Y”. A gene that was discovered in 1990 by molecular biologist Andrew Sinclair and who pointed out that its presence is a determining factor in male sexual development. It is, literally, the scientific father of the test that the IOC has chosen to integrate into its Olympic requirements.
But the thing is that he himself is against using it for this.
Your disagreement. This decision is not a big news, since if we look back, the body that governs world athletics, World Athletics, adopted this same test in September 2025 to participate in their competitions. Here is Sinclair himself He did not hesitate to publish an opinion article where he made it clear that the result is not definitive, since the only thing the analysis can say is whether the gene is present or not.
Because. In this way, it must be detailed that being positive in SRY does not give us information about whether it is working to form a testicle, if it stimulates the production of testosterone or even if it expresses the necessary receptors so that testosterone can be used.
Put another way: knowing that an athlete has the SRY gene does not tell you anything conclusive about her physiology, her hormonal levels or, by extension, about her supposed competitive advantages from having testosterone. The biology of sexual development is infinitely more complex than the presence or absence of a genetic marker, which will now mark the ‘everything’ before the IOC.
There is more evidence. This researcher is not the only one who opposes this decision, since at the beginning of March it was published an article signed by 34 academics to respond to the decision of World Athletics. Here they pointed to the same thing: we are facing a test that reduces everything to a single gene when biology is much more complex. And biological sex is the result of a very complex interaction of human genetics, hormones, receptors, tissues…
Furthermore, the IOC’s argument suggests that this test protects against competitive equity, but for academics, they point out that there is no solid scientific evidence to demonstrate that the presence of the SRY gene is directly related to having a greater sporting advantage.
It’s not something new. Although we now see a big scandal in the sports world over this decision, the reality is that if we look at the newspaper archive, something similar was already being done in the 90s. 30 years ago The IOC decided to require women to verify their sex through chromosomal testing and also by determining the SRY gene. But finally the tests were withdrawn due to technical limitations, the absence of medical evidence and also because of the legal problems it could have.
A Spanish case. Due to these tests, the Spanish athlete María José Martínez Patiño was disqualified in 1985 after testing positive in the chromosome test despite not having any physiological advantage over her peers. In this way, her career was practically doomed, but she was able to recover it thanks to the help of a geneticist who was able to document her case with scientific evidence that showed that it was not giving her an advantage over the rest of her competitors.
The debate. If the basis for requiring genetic testing is to protect competitive fairness, we must ask what science says about the real advantages of transgender athletes. And at this point much less is known than the general population believes.
One of the most important studies It was made in 2015 by a transgender researcher who analyzed the running times of eight athletes before and after their transition. In this case, the brands slowed down and their relative performance compared to runners of the same sex remained quite stable.
An IOC study. Published in 2024 and partially financed by the committee itself, produced results that do not fit with the discourse we keep hearing: transgender women showed worse results than cisgender women in lower body strength and lung function. But logically it does not mean that there cannot be residual advantages in certain sports, which is something that to this day remains a question that needs an answer.
And now what? We are undoubtedly facing a dispute about which tools are valid to solve a genuinely complex problem. Right now, science suggests that the SRY gene test is not the best tool, but because it does not give us a complete answer, since the SRY gene may be present and the body may not respond to testosterone. But this is something that today must continue to be investigated to obtain evidence that can guarantee this equity, but always with a scientific basis behind it.
Images | Umanoid Erik van Leeuwen
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