aside from being cissexist the whole XX = female and XY = male thing is Straight-Up Wrong
AFAB people can have XO, XXX, XXXX and XY chromosomes while AMAB people have have XXYY, XYY, and XX chromosomes and since the majority of the population never has their karyotype examined, they’ll never know that they have one of these chromosomal quirks unless that specific combination has associated symptoms, and not all of them do. you could literally have one of the aforementioned combinations without even knowing it and meanwhile you’re insisting that all AFAB people are XX and that anyone else who has this must also be female
we could also talk about how hormonal patterns for XX persons can naturally and biologically mirror that of a typical XY person, or vis versa, which gives rise to things like androgen insensitivity disorder. here u have it, folks, an whole group of intersex people who have XY chromosomes and testicles and vulva and vagina, all grown naturally, all at the same time.
the number of people who are intersex mirror the number of people who are born with red hair, but no one goes around trying to say that red isn’t a natural hair colour just because the phenotype doesn’t manifest in the majority of the population.
gonna ramble for a bit because this was one of my MOST favourite things I learned about in genetics. This was something I’d wanted to know all up until 3rd year and I had asked around my friends/classmates and everyone was like “no way, no, the X and Y chromosomes can’t cross over in meiosis, they’re different chromosomes!” and this always bothered me because. Of course they pair up! They need to pair up, else how would they separate properly? And by that measure, of course some crossing over would have to happen, because that’s just the way it goes.
So some people narrowed it down like oh maybe just the homologous areas can be recombinant. And maybe this was why I was so blown away when I learned this was wrong! That the region with the SRY gene can actually be transferred to the X chromosome - which happens RARELY but it can still happen and it was like!!! The gender distinction was just ripped away and I was kinda like wow. Wow everyone has genes that different people of any gender can have on or off. High or low. And biological sex is part of that. It’s variable. And I just.
(I feel like I should add that people that are born XY female (Swyer syndrome) and people who are born XX male (de la Chapelle syndrome) are born sterile but w/e)
science. genetics. gender. so cool.