Why do women have periods

View full lesson: A handful of species on Earth share a seemingly mysterious trait: a menstrual cycle. Were one of the select few mammals on Earth that menstruate, and we also do it more than any other animal, even though its a waste of nutrients, and can be a physical inconvenience. So wheres the sense in this uncommon biological process TEDEd describes the history and evolution of menstruation. Lesson by TEDEd, animation by TEDEd.