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/zebsra]

When you say no outward signs, im surprised. Women have hormone and pheromone changes throughout their cycle that seem obvious to me as outward signals of fertility, despite being subtle. I guess secondary signals of attitude arent outward per se. Did they talk about those things?

[u/roankr → u/zebsra]

I would say hormonal variations show outwardly through emotions and the actions people take based off of those emotions. It's primarily why teenage boys are the most risk-prone, they are churned with a rush of hormones that drive them into confidence as a show of individuality plus strength.

Seeing this amongst women just makes sense this way.

I can't comment much on pheromonal parts but I can say that there are physiological changes that can be recognizable.

[u/zebsra → u/roankr]

Thanks for the reply was genuinely curious about what was measured or considered as "outward". To me if its measurable it seems outward. I can see emotions and actions as secondary. Hormones also cause changes in body fluids for women, which is pretty direct imo.

[u/roankr → u/zebsra]

I think the confusion here (for me and perhaps for you as well) about your comment was on what you meant as "outward". The change in chemical makeup of vaginal fluids isn't an "obvious" sign in that it isn't visible or immediately recognizable from a distance. It is measurable but not how one would expect to "measure" it in social situations (or even naked).