“controversial theory that human beings are born as one of two distinct sexes, male and female.”
I once knew a person who was a hermaphrodite. They had both male and female parts. Thus they were not born as ONE of TWO DISTINCT sexes, but as a category called inter-sex. See link below and how legalities can get messy.
https://en.wikipedia.org/wiki/True_hermaphroditism
In the past what was usually done is that the penis was removed to make the person one sex. However in some cases the hermaphrodite wanted to be male. So a hermaphrodite was actually one of two sexes. You can’t force the wrong sex on him or her or unhappiness and depression will follow.
Biology is what it is -- people don't get a vote on what gender they are.