Menstruation (mammal)
Menstruation in mammals is the shedding of the uterine lining (endometrium). It occurs on a regular basis in uninseminated sexually reproductive-age females of certain mammal species.
Yanomami women
The start of "menstruation" symbolizes the beginning of womanhood. Girls typically start menstruation around the age of 12-15. Girls are often betrothed before menarche and the marriage may only be consummated once the girl starts menstruating, though the taboo is often violated and many girls become sexually active before then. The Yanomami word for menstruation ("roo") translates literally as "squatting" in English, as they use no pads or cloths to absorb the blood. Due to the belief that menstrual blood is poisonous and dangerous, girls are kept hidden away in a small tent-like structure constructed of a screen of leaves. A deep hole is built in the structure over which girls squat, to "rid themselves" of their blood. These structures are regarded as isolation screens.