Menstruation may be considered the endocrine equivalent of miscarriage. In both menstruation and miscarriage endometrial shedding is provoked by the sudden decline in estrogen and progesterone that occurs when fertilization or implantation fails to take place or is defective. The monthly bleeding is therefore the result of repeated reproductive failure since in a free natural setting women would be either pregnant or lactating ad libitum hence amenorrheic. Menstruation has become an obligatory feature of life for civilized women who are educated to accept the monthly bleeding as a price to pay for avoiding pregnancy. This "avoidance of conception" does not occur naturally since sexual activity in nature is predominantly associated with ovulation a condition that renders females both attractive and receptive. In order to avoid conception civilized women had to learn how to minimize their sexual attractiveness while retaining their enhanced social magnetism during ovulation by bathing using deodorants and perfume and covering their bodies as completely as possible. Whenever they succeeded in avoiding sex during ovulation they then had to deal with the inevitable bleeding that would ensue. In the beginning they had to hide during menstruation secluding themselves in a separate room or location as women of many indigenous tribes still do today. The development of fabrics such as cotton silk and linen led to the creation of sanitary protection which could be replaced at regular intervals. (excerpt)