From Scientific American:
Needing a bathroom break is basic biology—Caitlyn even posted her video with the hashtag #everyonehastopee. But as the science of transgenderism advances, it seems that being transgender is basic biology, too.
Usually, when we ask questions along the lines of “why are people the way they are,” the answer falls somewhere between “nature” and “nurture.” Being transgender, however, seems not to be one of these things. While the research is still in its infancy, so far, the answer is overwhelmingly: nature. How do we know? While the biological basis of transgenderism is still being uncovered, there are some leads hotter than Lea T’s outfits.