To educate others reading this, it's far from "obvious" how to classify gender in sports. Checking if they have the right "parts" physically doesn't do it. Checking for hormone levels doesn't do it. Even checking for Y chromosomes doesn't do it.

In my opinion the way forward is to stop trying to find arbitrary ways to define gender, and just start making competition classes based on whatever factors are relevant to the event. E.g. a women with high testosterone? They can compete with men or women with the same testosterone bracket. This would also let men with low-T compete fairly rather then be excluded from the games.

It's also relevant at what point other genetic changes are "unfair." There are absolutely genetic traits that give people HUGE advantages in various competitions. Just like the gender-related properties, these are natural and yet result in unfair competitions.