Small but important point: I’ve never said there are only two genders. There are innumerable gender identities.
The question at the heart of this debate is whether sex or gender identity should form the basis of decisions on safeguarding, provision of services, sporting categories and other areas where women and girls currently have legal rights and protections.
Using the words ‘sex’ and ‘gender’ interchangeably obscures the central issue of this debate. If you’re interested in what I actually said, see https://www.jkrowling.com/opinions/j-k-rowling-writes-about-her-reasons-for-speaking-out-on-sex-and-gender-issues/ (in which I literally say ‘trans lives matter’ and ‘trans rights are human rights.’)
Previous writing: « J.K. Rowling on the Magic of ‘Things’