Menstruation: The Aftermath of an All-Natural But Ruthless Embryo Screening

Most animals don’t menstruate. If they don’t use their uterine lining, they simply reabsorb it. Only bats, monkeys, and apes take the drastic and seemingly-wasteful step of pitching out the entire thing. And humans toss it out more often than any other animal.


This Ted-Ed video outlines one hypothesis for why menstruation evolved–it’s the aftermath of a strict screening process that selects embryos best able to invade uterine tissues and start manipulating their mother’s metabolism.

[Ted-Ed | Emera et al. 2012]

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Wow, what a hack job. It’s held together with chewing gum and baling wire! It’s a wonder it works at all! Proof positive that natural selection is a blind tinkerer, not an engineer.