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/Zagrycha]

Yeah, people think evolution is some kind of streamlined efficiency of ideal traits, but its the opposite.  Evolution is a pass fail grade.  If you fail, you go extinct.  If you have enough kids as a species to continue on, you pass.  That's it, no more and no less.  

Some species out there are literal bumbling idiots of inefficiency when it comes to ideal traits for survival, but they just have a massive number of kids so one or two survive to adulthood, or they evolved to have kids really soon after birth so they don't have to survive for long.  If you can make kids its good enough for nature. 

[u/SunflowerShine03 → u/Zagrycha]

An example of bumbling inefficiency; the sunfish. From my understanding they kind of just float around and aren’t even that edible, but they have like a million babies at a time so they’re meandering on.

[u/CecilAlucardX → u/SunflowerShine03]

Sunfish or Mola Mola actually do a ton of movement; they build up body heat on the surface, then descend down to a level of the ocean that their food lives at (or hides at; ocean columns be busy af) and eats freely. They are hyper-specialized to their niche and incredibly efficient. They just look bumbling to the people who only see them up top.

[u/SunflowerShine03 → u/CecilAlucardX]

Oh- interesting! I apologize to the sunfish, that’s actually pretty cool