EDIT: I probably should have said why does *menstruation* last so long
I know every women is different and this doesn’t apply to everyone, but many women experience 2 heavy days, 1 medium day and then 2 extremely light days. How come our bodies can’t rid it all in 3 days instead of dragging it out into 5 with 2 almost pointless days?
In: Biology
Likely because it doesn’t matter that much that it’s so long. Evolution doesn’t select for the most convenient thing, it selects for the most advantageous thing and if something is annoying but not harmful, it’s not going to selected against by evolution. The reason it didn’t matter to have a 5 day period for most of human development is that periods used to be quite infrequent. With no birth control and with the greater exercise and less rich diet of Paleolithic times, a woman might menstruate 50 times in her entire life. A heavier period might even have meant a greater chance of pregnancy because it discouraged people from having sex when not fertile, meaning more sex during fertile days of the month and greater odds of pregnancy.
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