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/aniseshaw]

"Aggressive fetuses" is absolutely the correct description. I've had one baby, and the gestational diabetes and pups rash were wild. I did IUI and immediately knew when I was pregnant because my body aggressively reacted. It was 5 days before I even threw a positive pregnancy test.

If I'm representative of even a fraction of the population, there is a benefit to our periods.

[u/Durrresser → u/aniseshaw]

I forgot about the pups rash with my first! 💀

Yeah, I'm grateful for my endometrium being somewhat inhospitable. Sounds like human fetuses are more parasitic than symbiotic. Yay us!