If gender is a social construct, how can genders outside that construct exist?
If gender is an innate part of humanity, how does a spectrum even function on a psychological level? What's the difference between these non-binary genders and binary ones? etc etc
This is not the easiest thing to explain. I'm having some trouble coming up with the right words.
Construct means it's not inherent, but in some way created, right? Maybe it's part socialization, part psychology, part biology, but some element of it is sustained because of choice, because of decisions we make. We can choose to have genders that have not been represented in our cultures before. We can construct gender to fit with our understanding of it. Basically, we can control what gender is and what it means because it's our construct. So to have a nonbinary or genderfluid person is just as acceptable as a female or male person. None is more natural or unnatural than the others.
Of course we have our cultural heritage, all our history, tapping us on the shoulder and saying "Hey, but wait. Male and female only." We have old science saying that there is only male and female because that's from a time before we even had an idea of psychology, before we understood chromosomes and hormones. We're carrying around this very old idea that gender=sex and that there are only two options.
Is gender innate to humanity? Maybe. It's certainly a part of culture, and most people are raised within a culture. And humans also have their personal biology (with the hormones and chromosome and sexual characteristics) and that's about as common as having culture. So it's hard to say. What would a group of people raised without sexual organs and without culture think of gender?
In a way gender is just a social ordering based on characteristics which we loosely group into two categories. We look at people's bodies and say: "You belong in Group A, you belong in Group B." The effect of having this reinforced most of our lives is going to affect how we think of ourselves, how our brains are wired, so it will have a physical affect on us.
Now, maybe some people will have experiences growing up that are different from the common experience. Maybe some element of their biology (how they develop in puberty, what their genitalia look like when they're born, how their brain chemistry is set up at birth) which will make them not feel like they fit in with the category they're placed into. They'll want to be in the other category, or no category, or a category you didn't conceive of as a possibility. A lot of it comes down to comfort with identity. Lots of people are okay with the idea of being called and thought of a a male or a female. It doesn't bother them because it aligns with their biology/psychology/socialization. It's no problem for them. But not for everyone. And for the people uncomfortable, well, gender isn't necessary, it isn't enforced by some higher power, so why can't it be changed to incorporate everyone if we, as the human race, insist on having and using gender?
Like, imagine you have a fill out a form and it asks you to state your ethnicity. If the categories are only "white" and "black" and you're brown then what are you going to do? Do you pick one and just hope it'll work out or do you insist on their being another category?