In 1993 Margie Profet, an evolutionary biologist from the Universityof California at Berkeley, announced that she had figured out a betterexplanation for why we menstruate than the traditional idea that the uteruslining didn't get used, so it had to go somewhere. She says that the ideathat we bleed every month just because we didn't get pregnant has botheredher since she saw her first sex-ed films in school. As an evolutionarybiologist, she believes that our every function should contribute in someway toward our survival as a species, and bleeding for no good reason justdidn't make sense.
Her theory is that menstrution fights disease, that it keeps infectionsout of the uterus. In a nutshell, she believes that sperm which enter theuterus after sex carry bacteria which is potentially harmful, and couldbe absorbed through the walls of the uterus. During the process of menstruation,the bacteria are flushed out of the body along with the lining of the uterus,and the blood flow which accompanies the flushing also contains immunecells called microphages which attack any lingering bacteria.
Profet's theory has caused a lot of controversy in the scientific community,and it will be a while before we find out if she is correct. Even if sheis proved wrong, the new attention she has brought to the often ignoredsubject of menstruation is valuable in itself.