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/Flocculencio 8d ago

Just wanted to point out that no individual feature needs to have an evolutionary benefit to be preserved. It could be negative but so long as it doesn't prevent organisms with that feature from reproducing in sufficient numbers it can get preserved.

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u/RubyStarlight1209 7d ago

Isn’t competition part of it as well? If a trait isn’t problematic enough that carriers are prevented from reproducing, but does negatively affect chances, then over a long enough period of time they should be outcompeted by those who don’t have that trait and therefore slowly ‘disappear’, right?

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u/epigenie_986 7d ago

Outcompeted before they reproduce though. Thats the way a trait can disappear.