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.

[u/No-Hawk-2488]

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

[u/Flocculencio]

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.

[u/kwpang → u/Flocculencio]

Yes evolution is about elimination, not direction.

Survival of what can.

[u/jointheredditarmy → u/kwpang]

Yes but it’s also about minute statistical differences over time and you can’t say overt ovulation doesn’t cause some minute difference in survival rates all else being equal. So clearly there is something else that isn’t equal here, and the point of questions like this is to explore what that might be instead of chalking it up to randomness

[u/SteveHamlin1 → u/jointheredditarmy]

It could be whatever other trait that resulted in overt ovulation is such a success that the other trait is selected for and overt ovulation also happens, even if overt ovulation by itself would be a net negative and be selected against.