I think you're confused. There are only two sexes, male and female. Sex is what you were biologically born as from birth, while gender is what you choose to identify as. Gender is a choice, sex isn't. They couldn't discover any other genders because at the time they probably didn't even know what gender was like three thousand years ago, therefore they couldn't look like a different gender.
im pretty sure its adaptation <3
They are related because genetics change during evolution.
Another name would be <span>tropical grassland</span>
