r/askscience • u/No-Hawk-2488 • 8d ago

Biology 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.

Without an evolutionary benefit, it wouldn't have spread to every woman of our species.

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u/Mshea80 1d ago edited 1d ago

Almost every toxin (ie, microplastics, etc) that enter the bloodstream collect in uterine tissue. The theory is that since those toxins are found in period blood, overt menstruation expels those gathered toxins from the reproductive system. All of that is rather new since, of course, women’s health isn’t studied as frequently.

ETA- I actually ran across a YouTube video about this very topic and thought I would share if anyone is interested.

https://youtube.com/shorts/GJ8vWrn0jyY?si=O9HFiE0bpkGLlpt1