How did human ancestors get confused into thinking there were only two genders?

 They didn't have Tumblr and Reddit to guide them, and instead had to rely on biological reality.

EDIT - Deleted as “hate speech”, restored on appeal. Hate speech against whom? Mythical cavemen? 

It must have been terrible; imagine believing that there is only male and female! One wonders how they got by without the enlightened and productive gender-obsessed supermen that have taken our modern society to the pinnacle of happiness and harmony.

No wonder those moronic cavemen only had fire and leopard skin pants; they didn't have any non-binary, agendered or transfemme people around to point out that reality is bigoted.

If only they had had gender studies instead of stone tools and the wheel, we would now be living in a biology-free utopia, where heteronormativity was ruthlessly stamped out as the hate crime it so clearly is.

Thank goodness that nowadays we have a legion of mentally ill teenagers who can't leave the house for fear of being misgendered and an army of virtue-signalling social justice warriors to tell us how bigoted we all are for not having a personality disorder and refusing to sleep with men in dresses who insist that their penises are in fact vaginas. Thank heavens that the writings of a bunch of paedophiles in the 1960s have been embraced as better than scientific fact, and that we can keep children young and ripe for abuse with puberty blockers and hormone treatment.

I'm so grateful to live in such an enlightened time, and look forward to the tyranny of reality finally being replaced by whatever nonsense the most vocal minority group is screeching for that month. Goodbye morality! Goodbye common sense! Goodbye man and woman! To the dustbin of history with you!

H/T to Ed in Moulton