Chromosomes Aren't Magic

Chromosomes Aren’t Magic

For the 157th time, I just saw someone define ‘female bodied’ as ‘anyone with XX chromosomes.’ All too often we get caught up in the idea that people can identify however they want, but biologically…

No. Just. No.

Thing is, X and Y chromosomes don’t actually do much in the day-to-day. They don’t cause mood swings, assertiveness, or determine your feelings on the color pink. They encode proteins, and that’s it. And by the time you’re born, the different configurations are all pretty much doing the same thing.

Y chromosomes contain only a few genes which are only really active during embryonic development. The X chromosome contains more genes, but we only need one X-worths ‘dose’ of those proteins. People with two X’s avoid overexpressing the genes on the X chromosome by folding one of those in each cell into a tight, unreadable little ball, called a Barr body.* So essentially, every person you meet has the same working compliment—1 active X—of so-called sex chromosomes. And those genes? They code for things like cell membrane transport proteins, eye color, and other basic cell-building traits. Just to rub it in, there’s some crossover between X and Y’s during meiosis—chunks of DNA physically move from one to the other, then get passed on to your kids.

The thing is, when you point to someone’s chromosomes as the ultimate arbiter of their sex (not to mention gender), what are you really saying? Have you tested their chromosomes? Have they? Probably not. Karyotyping costs hundreds to a few thousand dollars and is not routine. It’s certainly not unheard of for people to get surprising results, but that’s sort of beside the point of today’s post.

So what are your really talking about? Well, you’re assuming what that person’s karyotype is. Probably based on some much slipperier criteria -their sex assigned at birth (usually based on the appearance of their genitals as a baby), the sex you’ve assigned them based on their current appearance, etc. Traits that are…not so binary. Harder to defend as essential to one’s being, or you wouldn’t fall back on invisible traits. It’s kinda hard to pin the validity of someone’s identity to ‘well, your jawline is maybe kinda roundish, and you only have a touch of facial hair, so…Woman. Definitely. Forever.

Personally, I’m rather convinced that the reifiction of invisible, recently-discovered** chromosomes as the ultimate arbiter of sex has coincided with the downfall of other, more tangible signifiers. Genital shape? We can change that. Breast size? Body hair? Obviously a continuum, and also quite mutable. Prevalent hormone system? Changeable, and lots of cis people mess with theirs too.

The categories of ‘male-’ and ‘female-bodied’ are worse than meaningless. They deny not just trans* people’s identities, but often the the nuanced reality of our physical bodies, in favor of cissexist beliefs about how our bodies should look and function.

Relying on chromosomes as the ultimate arbiters of sex, and the genders that get assigned with them, is ultimately a political argument. It’s an attempt to pen people into inescapable categories, over their own objections or any other evidence—their own gender, how other’s perceive them, the details of their body. You’re saying that nothing that’s happened to them, nothing they’ve done or felt or experienced since being born, is relevant to who how they experience gender. And, frankly, that’s just ridiculous. Don’t ask us scientists to have your back when you make shit up.

*X-inactivation is what gives us calico kittens. Long story.

**The XY system was discovered in 1905 by a badass early geneticist named Nettie Stevens, by studying mealworm eggs. Her boss had missed the discovery by only looking at worm testes, never at female worms.***

***The XY system in insects actually evolved separately from the one in placental mammals, and is only one of many sex determination systems. Reptiles determine sex by the temperature in their eggs. Birds use the ZW system, where females are ZW and males are ZZ. Platypus sex is based around 5 different pairs of chromosomes, and papaya plants have recently evolved their own sex chromosomes from scratch, which determine which of their 3 sexes each seed will produce.
****This post was largely developed through conversation with dissimilarto

Edited to fix the formatting snafu and link—deletion my phone caused.