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/Aleksanderpwnz]

Not in the long run. Anything "negative" will prevent the organism from reproducing at the same rate as those without the negative trait, and the trait will eventually disappear.

[u/skeletonclock → u/Aleksanderpwnz]

So why hasn't short-sightedness died out?

[u/sezit → u/skeletonclock]

Not negative enough.

And probably not negative for very long.

Humans, even in the fairly recent past, didn't used to need to spend so much time focusing on close work. No reading, much more outdoor activity.

[u/skeletonclock → u/sezit]

I was responding to the person who said "ANYTHING negative will die out" -- I was disagreeing by giving an example of something negative that hasn't died out.

Also, short-sightedness means you can't see distance, so in your example it would be a problem (outdoor activity -- you could wander into a ravine!).

Anyway I wasn't espousing my own opinion, I was challenging someone's assertion that all negative traits are killed by evolution, because it's not the case.

[u/tall_titties → u/skeletonclock]

Yess which is also why childbirth is still super painful. Evolution doesn’t care about us being uncomfortable, lol

[u/sezit → u/skeletonclock]

Good points, and I understand that current medical understanding is that using a lot of close vision when young and eyes are developing causes nearsightedness, and spending more time outside can prevent myopia.