100% all humans at the Endo of the day.

The reason a lot of it exists is to communicate social roles, because social role mediates interaction. The earliest division of social role was biological sex, and so that's commonly an aspect in gender.
How gender is expressed is a complex interaction between socially agreed upon norms, how the individual interprets their gender, how others interpret that, and so on.
Individual gender is a matter of psychological, biological and social factors which influence how an individual chooses to understand themselves in the context of society and also how they present themselves to society.

The socialization part is where we teach people the behavior needed to express genders, and is where the genderd toys come in, amongst other things.

All that to say, what we need is a way to communicate social role, and what we have to do that is loosely tied to sex and dominated by an imnense amount of social momentum. In a sane world the genders would be split into a lot more pieces.