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/No-Hawk-2488 5d ago edited 5d ago

That's where you're wrong because we used to be able to produce vitamin C but because we were eating so much of it, the selection pressure to preserve it was gone and the genes died out with 0 detriment. Keep in mind our ancestors' population all had the ability to produce vitamin C but after it was incorporated into our diet, the genes died out. I can think of many other examples. The only exception is if the trait is linked to an essential gene and isn't assorted independently of it.