-Given the empirical reality of the different multivariate trait distributions, "Who are the best athletes _among females_" is a natural question for people to be interested in, and want separate sports leagues to determine. Including males in those leagues—even males on feminizing hormone replacement therapy—ruins that.
+[TODO: (clean up and consolidate the case here after reading the TW-in-sports articles)
+
+The "multivariate" part is important, because
+
+Different traits have different relevance to different sports; the fact that it's apples-to-oranges is _why_ women do better in ultraswimming—that competition is sampling a corner of sportspace where body fat is an advantage
+
+It's not that females and males are exactly the same except males are 10% stronger on average
+
+It really is an apples-to-oranges comparison, rather than "two populations of apples with different mean weight"
+
+https://www.lesswrong.com/posts/cu7YY7WdgJBs3DpmJ/the-univariate-fallacy
+https://www.lesswrong.com/posts/vhp2sW6iBhNJwqcwP/blood-is-thicker-than-water
+
+If you just had one integrated league, females wouldn't be competitive (in almost all sports, with some exceptions [like ultra-distance swimming](https://www.swimmingworldmagazine.com/news/why-women-have-beaten-men-in-marathon-swimming/)).
+
+]
+
+Given the empirical reality of the different multivariate trait distributions, "Who are the best athletes _among females_" is a natural question for people to be interested in, and want separate sports leagues to determine.
+
+(Similarly, when conducting [automobile races](https://en.wikipedia.org/wiki/Auto_racing), you want there to be rules enforcing that all competitors have the same type of car for some common-sense-reasonable operationalization of "the same type", because a race between a sports car and a [moped](https://en.wikipedia.org/wiki/Moped) would be mostly measuring who has the sports car, rather than who's the better racer.)
+
+Including males people in female sports leagues undermines the point of having a separate female league.
+
+[TODO: more sentences explaining why HRT doesn't break taxonicity of sex, and why "gender identity" is a much less plausible joint anyway]