Evolutionary theories were used by white supremacists to claim that white people were genetically predisposed to rule over others. That's a big part of what race science was. Their theories were wrong, just like how Blanchard's understanding of trans people is wrong. These theories weren't even ancient history, as there have been papers in the past 50 years that tried to claim black people had lower intelligence based on genetics.

What racial minorities have done is taken away the authority from these racist theories. Skin color and facial features are inherited via genetics, but race is a construction that tries to tie these traits together, often very inaccurately in an effort to support social oppression. Race is a crude and imprecise approximation of one's genetic lineage that people attach inherent meaning to. The essence of race comes after the material properties of the person.

The same is true for all categories and descriptions of reality; it's just more abundantly obvious in the case of race. Even the most fundamental theories of physics are us applying essence to matter in an effort to understand it. We thought atoms were the smallest units of matter, that's literally what the word means. However, not only are atoms divisible, protons and neutrons are divisible while the negative counterpart to the proton, the electron, is not. Physicists try their best, yet there are still things they know they don't understand.

As we go higher up the chain of complexity from physics, from chemistry to biology to neurology to psychology to sociology, it becomes obvious that things cannot be clear cut or absolute. As I said before, only sex cells are really binary, with everything else being based on incentives. However, even that binary probably came about because of an incentive to have unequally sized sex cells over equally sized sex cells. There just isn't a powerful enough incentive for sperm and egg cells to equalize in size capable of overcoming the incentives for the sperm to be as small as possible.

Where was I...?

Oh yeah, gember!

Gender, similarly to race, is an approximation of traits. Unlike race, the traits influence one's preference or willingness to be seen and thought of as specific genders, both by other people and by themselves. Those traits seem to influence what gender they are comfortable with or can even tolerate, although we have no idea what they are or how they work. We probably won't figure them all out any time soon, and we probably shouldn't assume we ever understand all elements of it. Gender differences are more correlates of one's gender, and we cannot expect to establish causality in any ethical way.

I also believe that one's internal gender works more like a range of acceptable identities and expressions rather than a single fixed point. It's probably the case that many cis people would tolerate or even prefer being somewhat off the binary, as well as their assigned gender. If cis people experimented, many of them would be happier using they/them or neopronouns in addition to their cisgendered pronouns. Many cis people enjoy gender bending expression while not identifying as the other binary gender or as nonbinary. One doesn't need to conform their identity, pronouns, or expression to each other.

That said people will generally prefer there to not be great dissonance between their expression/pronouns/identity. If somebody feels happier presenting as a man everyday and being referred to with he/him pronouns, it's unlikely for that person to be an entirely cisgender woman in the long term. As more binary trans people like myself can attest, some genders just aren't right for us. I couldn't be he/him and not feel like shit. Power to the people lucky enough to have multiple genders they feel comfortable with, but that's just not me. I tried they/them and being off the binary, but it was not the same as being a girl. I don't want to be seen as anything else and I don't have a choice.