Thread by @bschillace

Since yesterday’s tweet (where I broke down a scientific study JK Rowling posted about blood/sex/gender), I’ve seen the argument that ‘sex is real’ because of chromosomes used to support anti- #transgender rhetoric. So today I’m sharing some biology in support of #TransRights

Let’s consider chromosomes first. The anti-trans argument says XX is female/woman and XY is male/man. That’s the gender binary. But biology isn’t binary—it’s messy. You can be born XXY or XYY. You may be born with aspects of both sexes along a spectrum. It’s also true for animals

A true XXY, what we call Klinefelter syndrome (47 chromosomes). 64% of those with the condition are never diagnosed (Jeannie Visootsak, MD, MSc 2014) and most who are only notice in puberty. About 1 in 500 are born with XXY. Now, XYY occurs in about 1 in 1000.

In both XXY there are changes in secondary sex characteristics. XXY often develop breasts, but may also have a penis. Some are raised as girls and some as boys. XYY tend to be taller and develop mostly like XY. There are also XXYY variants. But wait! It gets more complicated!

Some people are born intersex. That means having some or all of the sex characteristics of both XX and XY. BUT!! You don’t have to have an extra chromosome for that to happen! An XY or XX person with 46 chromosomes may be born with ovaries and testicles, penis and mammary glands.

To make it more complicated, sometimes in an XY fetus, the Y doesn’t turn on (Swyer syndrome) The baby appears as XX, is usually raised in accordance with perceived binary as a ‘girl’ and may not realize they have a Y until puberty or—in some cases—when trying to get pregnant.

Variation in nature happens all the time. Human prejudice tries to say it’s pathological. It’s estimated there are 70 million people with variants, either chromosomal or intersex, and considering many with XXY and XYY don’t even know, it’s probably higher. What does this mean?

It means, yes, ‘sex’ is real. But it’s not binary, and it doesn’t fall into neat gendered boxes. When anti- #transgender people use it to argue their cause, they have the wrong end of the #science stick. The spectrum of biological variation supports fluidity. #TransRights