I focused on those athletes because they’re the motivating factors behind this decision. DSD males and trans women both have the innate advantage of male puberty, which is why the IOC is making this move. To focus specifically on trans women, here’s one example out of many on why we have separate competitions for men and women (not a sympathetic article, but factual):

https://quillette.com/2025/10/30/the-scandal-of-ana-caldas-and-the-case-for-sex-screening-in-female-athletics/

In 2016, a Portuguese-American athlete named Hannah Caldas participated in the female category of the “Monstar Games,” a large fitness competition held in Rio de Janeiro. The Games included a weightlifting challenge run by Brazil’s Fortify Equipamentos sporting-goods retail chain, whereby contestants were scored on how many times they could lift heavy balls over their heads in the space of a minute.

An event official asked Caldas to choose between one of two balls—weighing thirty and seventy pounds, respectively.

“How about the 120?” Caldas replied, pointing to a third, much larger ball.

According to Caldas’s subsequent recollection, the official explained that this wasn’t a realistic option for contestants registered in the female category, since “no girls had been able to pick it up.”

“Challenge accepted!” Caldas later wrote on Instagram. While a fellow athlete named Joyce Rodrigues filmed, Caldas proceeded to heave the 120-pound weight into the air no fewer than sixteen times.

The idea that biological males don’t have an athletic advantage over females is plainly, obviously wrong

USMS records indicate that it was 23 January 2009 when a new swimming sensation identified as “Hannah Caldas” suddenly appeared on the women’s USMS racing scene. Despite being a complete unknown, Caldas immediately began dominating the competition in the 30–34-year-old age group—including winning five out of six events at Caldas’s inaugural tournament in Charlotte, NC. The performances were so astounding that Caldas reportedly almost hit a benchmark time for Portugal’s women’s Olympic swimming team (missing the cut by a mere 0.3 seconds).

This would be a shockingly impressive athletic run for anyone—let alone a (nominal) rookie such as Caldas, who was able to blast past former NCAA swimming stars with ease despite having no collegiate training as a female athlete; and who was, by this point in life, a full decade past the prime age for Olympic-calibre swimmers.

That’s why the argument that trans women are only 0.X% of competitors doesn’t hold any water. They can still dominate a sport and deny medals to any cis women competing. This is now becoming an issue at the Olympic level which is why the IOC is addressing it, but people have tracked many more cases at sites like https://hecheated.org/. Whether or not you like the people behind that or similar sites, it’s more about the facts.