
sex is complicated, and while chromosomes are definitely part of the equation, hormones and physical parts are more important. Generally, your dna tells your body what hormones to produce, and your hormones in turn shape your body. Change what hormones your body gets, and you change quite a bit of how it operates. Surgery obviously changes even more. People will disagree on definitions of sex, especially if they consider it fully binary, but I would say those physical changes affect sex
chromosomes aren’t deterministic of sex, sex is a complex multivariable phenomenon. the reason that culturally the most prevalent definition of sex revolves around chromosomes at this time is because of transphobia, because they are the only trait that cannot be changed. the vast, vast majority of people have never been karotyped—yet their sex is not “indeterminate”, it’s based on observed primary and secondary sex characteristics.
1) You can’t tell someone’s chromosomes just by looking at them: there are more than just different chromosome combinations, and expression varies too. 99% of the US has not been karotyped, as someone on the other thread pointed out. 2) chromosomes don’t determine your “biological sex,” there are cis women with XY chromosomes. They have other conditions that caused them to develop “female” primary and secondary sex characteristics, and they are considered “biological women”
there are a variety of intersex traits, one of which is androgen insensitivity (it’s a spectrum). this causes someone with XY chromosomes to develop as a “female”, their body literally does not respond to androgens/testosterone. they are XY cis women. the olympics introduced chromosomal sex testing for women and then had to get rid of universal screening in the 90s because it flagged zero cases of “male imposters” but would routinely identify and flag intersex women—many of whom didn’t know.
after the olympics dropped their universal testing policy, they still made it possible to “challenge” specific athletes and request they be tested. there’s a lot of data showing how this policy was often enforced in racist ways (women of color, especially from the global south, faced disproportionate scrutiny and testing).
the IOC/international governing bodies briefly developed guidelines based on testosterone (still imperfect, but not based on chromosomes), due to increasing transphobia worldwide they have now reverted to testing for “genetic sex” (iirc they’re screening for the SRY-gene, sex-determining region on the Y chromosome). which again, by itself is not deterministic of “sex”. there are even XX cis men that have a stray SRY-gene in their dna which caused them to develop as “male”.
i hope this helps and also provides some real world context for the stakes around defining “biological sex” and how it is actually impacting and harming trans people (especially trans women), intersex people, and women of color. i understand a lot of queer people don’t gaf about sports, but many of us do, and most importantly excluding trans people from sports means justifying our exclusion from public life—especially for children.