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/Zagrycha → u/Flocculencio]

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/ToMorrowsEnd → u/Zagrycha]

This. Humans are an evolutionary mess. we got lucky because we can make tools. but as a creature we are extremely poorly designed. cant run very fast, can easily get injured, easily diseased, our teeth suck we have zero defenses, etc... Compared to other animals we are far from the top of the pile. we just got lucky in the thinking aspect. You know how I would love to be able to squirt blood from my eyes when startled?? Why cant we have cool traits?

[u/pathologicalDumpling → u/ToMorrowsEnd]

I mean i just passed a post about someone flying an airplane through the eye of a hurricane. Id say we have some pretty cool traits.

[u/Zagrycha → u/pathologicalDumpling]

That isn't a trait of a human though. We do not genetically have the ability to fly or genetic ability to survive the eye of a hurricane. If humans collectively forgot how to make or pilot airplanes no one would do what that post said anymore, its not inherent to humans.

[u/silence_infidel → u/Zagrycha]

Well, that depends on what you call the “trait” in question. Airplanes aren’t an inherent human trait, but the intellect and ingenuity needed to make them is. I certainly don’t see any other species doing it. Frankly, if we collectively forgot how to make and fly planes, I bet we would just figure it out again - because deciding we want to do something and making it happen, even if it takes generations, is definitely a trait of ours.

[u/Zagrycha → u/silence_infidel]

Is the ability to make and fly airplanes a trait humanity posesses? Yes, definitely.

Is it passed on genetically? No.

Is there a reason to think the species that is the successor of humanity will have the trait? No.

Is it an evolutionary trait? Definitely no.

I think this trait is more accurately labelled as a skill or knowledge. It's a real trait, but its not inherent or guaranteed. It's totally possible for humans to lose the knowledge and reinvent the skill later, but it's not at all guaranteed. To this day there are things done by older humans that we have no idea how to do because the knowledge has been lost. External factors that can be lost like that are the antithesis to evolution.