To expand on this, I say that the existence of transgender folks proves that there is biological reality to gender. Think about it, if it was just social conditioning, infants must be an agendered blank slate, with their identity constructed over time by conditioning. But some individuals just know from an early age that the gender that they were presumed to be is wrong. Not just wrong, but wrong, and they are most definitely something else. There’s clearly another force at work than nurture, which must be nature.