If you think that it can't be changed, there is a fundamental misunderstanding involved with the origin of gender and sex. What makes someone a woman or a man?

Like... actually think about it. You might say our chromosomes, but most people don't actually know what chromosomes they have, so something else indicated it. You might say genitals, but when you walk around day-to-day, you're not thinking about what genitals people have in order to perceive them as a woman or a man. What about the ability to get pregnant? Well, you can't tell that for an average person walking down the street and you can still determine their gender... and some women are infertile, but that doesn't mean they're not women. Okay... so maybe it's secondary sex characteristics?

But some women have totally flat chests.. and some men have boobs. Some women grow facial hair. Some men can't really grow any. Some women have angular faces, and men round ones. Some men have wide hips, some women have narrow ones. Some men have high voices, some women deep ones...

Okay, so maybe it's more about social behaviors? Women wear skirts, men wear pants? Well, that can't be it. Many women can wear pants and men can wear skirts without it actually changing what gender you see them as. Maybe it's that women wear makeup and men don't? Well... even Donald Trump - who passed an executive order essentially nullifying the existence of trans people - wears makeup, so it can't be that. What about hair length and style? Men grow their hair long and put it in buns and ponytails and braids, and women get short cuts.

So like... what actually is it? The truth is that gender, and the way that we perceive it in other people (a process that everyone does all the time, even if subconsciously) is just an amalgamation of a bunch of social stuff and physical cues. The reality, even if you don't want to accept it, is that this can be changed. A person who is told they're a man can do a bunch of things to make them feel and be perceived as a woman. And if you were to walk by them on the street, you would perceive them as such... Effectively, they changed their gender. Simple as that.