Sex and gender identity have been in the news, so you, like J.K. Rowling, might be wondering about the difference between sex and gender, or if sex is "real."
First of all, here's a vocabulary review so that we're all on the same page.
Gender identity is our internal sense of who we are (example: woman). It's different from gender expression, which is our external presentation (example: femme). Both of those are different from sex, which refers to our chromosomes, hormones, and genitalia (example: female). With me so far?
Now, sometimes, when people discuss sex and gender, they look to scientific research on these topics. They might end up touting biological essentialism, or the idea that there are two binary sexes (male and female) which ties people to a binary gender identity (man or woman). There's a very fine line, or no line at all, between biological essentialism and transphobia. Biological essentialism is particularly harmful because it makes it seem like there is basis to ignore the existence of intersex or non-binary people, when that's really not the case.
The science is abundantly clear: sex isn't binary. If you want to learn about this in-depth, we have a whole article on it.
But more importantly, scientific research should be irrelevant when it comes to treating people with respect.
In fact, research into the genetic or medical component of stigmatized identities might serve to further biases against marginalized people.
So, before you turn to science to defend transphobia, it's time to re-evaluate your biases.