The origin of menstruation is payback for the big brain
For a year, a woman, as a result of menstruation, loses a blood volume equal to half of all the blood in her body. In addition to the loss of blood cells, immunoglobulins, enzymes, hormones and other metabolites of the body, monthly menstruation depletes the reserves of essential amino acids, vitamins and trace elements. What justifies such extravagance of the always thrifty mistress of nature? Why in elephants, cats and bitches, after the end of the cycle, the endometrium is absorbed and absorbed by the body, and in women it is thrown out every time if it is not useful? Such paradoxes of nature have always piqued my curiosity, and I invite curious readers to unravel this mystery of the female body.
only these 3 species of placental mammals menstruate! More than 5000 species of the remaining placentals bypass the estrous cycle, which eliminates bleeding
To be precise, weak menstruation is found in only 9 more primate species and 2 species of bats. All are listed here:
Considering that the orders of Primates, Bats, and Afrotheria phylogenetically diverged in evolution about 100 million years ago, and menstrual bleeding is absent in closely related mammalian species, it should be recognized that the menstrual cycle is a fairly modern phenomenon in nature. Menstruation either provides an evolutionary advantage directly or is a by-product of evolution — a kind of “lower price” for a more substantial evolutionary acquisition.
In 1993, the hypothetical ability of menstrual blood to wash away the remains of the semen that carries the infection from the man was considered as an “immediate advantage”. On this hypothesis, the author was prompted by the correct fact – menstruating mammals have a higher sexual activity. But his interpretation of this pattern does not stand up to criticism – a 3-week interval between menstruation is quite enough for the development of an infectious disease, moreover, many microorganisms safely survive during the bleeding period.
Proponents of the “less pay” idea have also tried to look for signs common to humans, vampires, and jumper that may be related to reproductive function and cause menstruation. It was found that all menstruating species are characterized by:
High encephalization – large brain relative to body size;
Highly invasive placenta – fetal tissues are in direct contact with the mother’s blood (in other placental tissues of the fetus they do not come into contact with the mother’s blood to exclude an immunological conflict);
High sexual activity – mating before, during and after ovulation (other placentals mate 1-3 days during estrus, which corresponds to the period of ovulation).