https://blogs.scientificamerican.com/voices/its-time-for-a-world-without-gender/

The idea of gender is undergoing a revolution, as unconventional gender behaviors gain in acceptance. At the same time, however, virtually every societal move away from the gender binary—such as permitting gender-neutral designations on various documents—triggers a corresponding backlash.

These controversies bring to the fore a centuries-old question: how fundamental are sex categories? Do humans “naturally” belong to one of two groups, female or male, that are distinct not only in the form of their genitals but also in their brains and behavior?