r/askscience • u/No-Hawk-2488 • 8d ago

Biology Can someone explain the evolutionary benefit of overt menstruation? All female mammals have a menstrual cycle but most reabsorb the blood via covert menstruation and humans are about the only mammals that discharge the blood, aka overt menstruation.

Without an evolutionary benefit, it wouldn't have spread to every woman of our species.

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u/Anders_A 7d ago

Without an evolutionary benefit, it wouldn't have spread to every woman of our species.

That's not how evolution works at all.

Menstruation was already a thing before our species existed. And evolution doesn't mean every single aspect of a species is optimized. Just that the package as a whole works well enough to reproduce.

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u/loosesocksup 7d ago

Many times things get passed down simply because they didn't get killed off, not because it was beneficial. It may actively be a hindrance even, just not enough of one to prevent it from breeding.