Why are the world's fastest sprinters Black? Do Black people have an advantage over Whites? Should Black sprinters be banned from White people's races? Should there be a "Black" category?

If we concede that Black people have a physiological advantage over Whites, but do nothing about it, how do we justify a different approach to trans women? Do we just deny the Blacks' advantage because we don't want to open that box regarding other human attributes? Or do we rely on the difficulty of determining exactly when a trans woman "becomes" an athletic woman to say that we simply won't recognize the transition?

We have sports categories because they result in the greatest number of people participating and spectating. It's essentially a matter of natural selection: the structure that creates the strongest political consensus survives. Of course, political consensuses change. Whether this one will change remains to be seen. This article makes a good case, I think, that this one won't.