I’m not going to quote problematic points expressed in the introduction, but I want to provide additional context for “mostly binary”, which is somewhat misleading. Biological sex characteristics are also a spectrum, but with most people falling close to one of two points on that spectrum.
It’s fairly commonly known that a small but significant portion of the population is intersex, having prominent characteristics from “both” sexes. While this is often explained as anomalous, it’s only by degree.
I hope saying this is enough to encourage anyone reading my comment to not take my word for it, but to read this biologist’s Twitter thread[1] explaining in much greater detail than I could do justice, or rolled up by Thread Reader[2] for convenience as it’s lengthy.
I know this isn’t a popular format here, but even being familiar with the concept I found the thread very illuminating when I read it around the time it was posted and it’s a common reverence I use when this topic comes up.
[1]: https://twitter.com/sciencevet2/status/1035246030500061184?s...
[2]: https://threadreaderapp.com/thread/1035246030500061184.html