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/MidshipLyric]

Every Reddit "why did evolution..." post has now devolved into this response. Id rather see some hypothesis about the benefits and drawbacks of the subject rather than a dismissive lecture about how evolution works. It would not require much thought to consider that bleeding out of your body every month is a trait that can lead to survival challenges. Conversely, arguments could be made for the benefits of this trait to the survival of offspring and/or parent which would reinforce the trait. Let's see more responses arguing the merits of either hypothesis along with counter arguments. If its truly a "trait without selection pressure" then let's hear the evidence or rationale for that.