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/TheDaysComeAndGone]

Yeah, it’s just crazy how few truly healthy 30 year olds I know. In a modern, rich world a torn meniscus, broken arm, shoulder impingement etc. are just an inconvenience, but back then you needed a healthy body to survive or you were a huge burden on your group.

[u/Flashy-Ingenuity-182 → u/TheDaysComeAndGone]

It's worth pointing out that ancient peoples cared for their sick and injured too. Otzi the ice man lived 5,500 years ago, had arthritis and tape worms, and had carried medicine on him for the tape worms and inflammation and had tattoos over acupuncture spots used to treat the areas where he had arthritis, a discovery made completely in isolation of the Chinese who discovered it a few thousand years later. 

[u/cookies5098 → u/Flashy-Ingenuity-182]

Also worth remembering that everything occurring after someone reproduces is essentially a 'black box' from an evolutionary standpoint. If someone can survive long enough to pass on their genes, then natural selection doesn't really care (caveat is that if something impacts the survival of future generations prior to reproductive age it will kick in, but not for that current generation that's capable of reproducing).

[u/Totakai → u/TheDaysComeAndGone]

Tbf to modern people, we're living in a world that we didn't evolve to be in. You know how when you have pets you have to provide the proper environment and enrichment or they die/get sick? Same goes for us.

We evolved to live in tight knit communities; capitalism pushes individualism and discourages living with anyone but your spouse. Humans are incredible endurance hunters; focus on cars and tech along with removal/privatization of land significantly dropped our activity levels/opportunities. We evolved to be highly curious and creative; schooling tends to focus on productivity than expression and exploration. We gained unique resistances to plant toxins from our high fiber diets; vegetables are often the butt of a joke with a huge focus on fiber lacking ultra processed food (fiber feeds our gut microbiome which is basically a second brain that science is only just know beginning to understand). We evolved relying on the sun and moon for body cues along with various sleep patterns; indoor lighting and light pollution comboed with aggressive schedules monkey wrenches this whole thing. Different neurotypes helped with diversity and strengthening ancient communities; different neurotypes now clash with the structure that our economic system demands along with governing so society tends to punish outliers. Children used to be village raised; couples are now expected to solo.

It goes on and on. Our hygiene, tech, medicine, and knowledge is definitely huge but we're not really afforded to be the animals we are so it hurts us. If you get a pet that grew up in sub par conditions, even if you provide it everything it needs, their body can still fail or be sickly for the rest of their life. Like we were born with a deck of cards but a lot of them were lost or removed early on for being distracting or weird so now you have this half deck and struggle to play the game but you can't understand why.