Women

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April 10, 2026

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April 10, 2026

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"According to a recent hypothesis, menstruation evolved to protect the uterus oviducts from sperm-borne pathogens by dislodging infected endometrial tissue and delivering immune cells to the uterine cavity. This hypothesis predicts the following: (1) uterine pathogens should be more prevalent before menses than after menses, (2) in the life histories of females, the timing of menstruation should track pathogen burden, and (3) in primates, the copiousness of menstruation should increase with the promiscuity of the breeding system. I tested these predictions and they were not upheld by the evidence. I propose the alternative hypothesis that the uterine endometrium is shed/resorbed whenever implantation fails because cyclical regression and renewal is energetically less costly than maintaining the endometrium in the metabolically active state required for implantation. In the regressed state, oxygen consumption (per mg protein/h) in human endometria declines nearly sevenfold. The cyclicity in endometrial oxygen consumption is one component of the whole body cyclicity in metabolic rate caused by the action of the ovarian steroids on both endometrial and nonendometrial tissue. Metabolic rate is at least 7% lower, on average, during the follicular phase than during the luteal phase in women, which signifies an estimated energy savings of 53 MJ over four cycles, or nearly six days worth of food. Thus, the menstrual cycle revs up and revs down, economizing on the energy costs of reproduction. This economy is greatest during the nonbreeding season and other periods of amenorrhea when the endometrium remains in a regressed state and ovarian cycling is absent for a prolonged period of time. Twelve months of amenorrhea save an estimated 130 MJ, or the energy required by one woman for nearly half a month. By helping females to maintain body mass, energy economy will promote female fitness in any environment in which fecundity and survivorship is constrained by the food supply. Endometrial economy may be of ancient evolutionary origin because similar reproductive structures, such as the oviduct of lizards, also regress when a fertilized egg is unlikely to be present."

- Menstruation

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"How reliable is the woman's menstrual history in determining where she is in her cycle, namely that she is preovulatory? In a study by Novikova et al., they found the history of the first day of the last period to be unreliable 39 percent of the time (Novikova et al. 2007). In addition they found a wide range of cycle lengths with the first day of one period to the first day of the next to be 21 to 35 days. With a longer cycle the woman could be on day 17 of her cycle but still be preovulatory and with a shorter cycle she could be on day 13 of her cycle and be postovulatory. Although one may suspect the woman is approaching ovulation on pelvic exam with the presence of highly fertile mucus at the cervical os, it is impossible for a physician to determine whether the woman is preovulatory on a pelvic exam, in particular in a woman who has just been sexually assaulted. How reliable are LH testing and progesterone levels done stat in the emergency room in determining where the woman is in her cycle? The LH surge goes on over a twenty-four-hour period, and is usually detected by testing a first-morning concentrated urine. A random urine specimen, particularly late at night, may not detect the LH surge. In addition, serum progesterone levels are not emergency tests, and the results often are not available for twenty-four hours, even in major metropolitan hospitals, and even longer in small community hospitals. Therefore, this protocol may not have a timely progesterone level available to help determine if a woman is preovulatory in the emergency room."

- Menstruation

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"Three central contributions to the understanding of reproduction came from ‘’Blood Magic’’. First, it definitively challenged the image of a universal taboo which operated in the same way in all societies. Second, it argued persuasively against the idea that menstruation was marked because it was always linked to female subordination, based on associations with nature, the domestic, or the undervalued. Third, with nuanced case studies it demonstrated how menstrual fluids could be used in empowering ways, in love magic, in specially esteemed forms of cooking, in establishing and coordination a ritual calendar, and in providing images of creation and transformation. That volume did not, however, veer into the New Age fashion of glorifying menstruation, eclipsing mention of its reported dangers, or purging cultural associations with death, disease, and loss (cf. Owen 1998). Since menstrual bleeding is both a sign of continued fertility and of the failure to conceive in a particular month, its regulation is of great importance to female reproductive health, and a recently published volume (Van de Walle and Renne 2000) brought together work on the medical history of menstrual regulation and the “native science” of female fertility, especially its relation to herbalism. Many herbs were used as both emmenagogues (to bring on menstruation) and abortifacients (to terminate pregnancy), and the fundamental ambiguity about the purposes for which they were employed seems to have been an important element of their popularity."

- Menstruation

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"To Strassmann and others in the field of evolutionary medicine, this shift from a hundred to four hundred lifetime menses is enormously significant. It means that women’s bodies are being subjected to changes and stresses that they were not necessarily designed by evolution to handle. In a brilliant and provocative book, “Is Menstruation Obsolete?,” Drs. Elsimar Coutinho and Sheldon S. Segal, two of the world’s most prominent contraceptive researchers, argue that this recent move to what they call “incessant ovulation” has become a serious problem for women’s health. It doesn’t mean that women are always better off the less they menstruate. There are times—particularly in the context of certain medical conditions—when women ought to be concerned if they aren’t menstruating: In obese women, a failure to menstruate can signal an increased risk of uterine cancer. In female athletes, a failure to menstruate can signal an increased risk of osteoporosis. But for most women, Coutinho and Segal say, incessant ovulation serves no purpose except to increase the occurrence of abdominal pain, mood shifts, migraines, endometriosis, fibroids, and anemia—the last of which, they point out, is “one of the most serious health problems in the world.” Most serious of all is the greatly increased risk of some cancers. Cancer, after all, occurs because as cells divide and reproduce they sometimes make mistakes that cripple the cells’ defenses against runaway growth. That’s one of the reasons that our risk of cancer generally increases as we age: our cells have more time to make mistakes. But this also means that any change promoting cell division has the potential to increase cancer risk, and ovulation appears to be one of those changes. Whenever a woman ovulates, an egg literally bursts through the walls of her ovaries. To heal that puncture, the cells of the ovary wall have to divide and reproduce. Every time a woman gets pregnant and bears a child, her lifetime risk of ovarian cancer drops ten per cent. Why? Possibly because, between nine months of pregnancy and the suppression of ovulation associated with breast-feeding, she stops ovulating for twelve months—and saves her ovarian walls from twelve bouts of cell division. The argument is similar for endometrial cancer. When a woman is menstruating, the estrogen that flows through her uterus stimulates the growth of the uterine lining, causing a flurry of potentially dangerous cell division. Women who do not menstruate frequently spare the endometrium that risk. Ovarian and endometrial cancer are characteristically modern diseases, consequences, in part, of a century in which women have come to menstruate four hundred times in a lifetime."

- Menstruation

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"In societies where women might have their period only every two years or so because of frequent pregnancies and long breastfeeding, there might be fewer negative associations with menstruation, says Alma Gottlieb, professor of anthropology and gender and women's studies at the University of Illinois and author of Blood Magic: The Anthropology of Menstruation. "Yurok, a native tribe from the northwest coast of the United States stratified by class, had a group of aristocratic women who saw their periods as a time for purifying themselves," she says. As many women living in close proximity do, this group had their periods at the same time each month. "They were on a shared menstrual cycle and did a series of rituals during the cycle that they said was a period of their most heightened spiritual experience." The Rungus women from Borneo, she says, are pretty blasĂŠ about their periods. "They don't say it's pure, they don't say it's polluting," says Gottlieb. "It's just a bodily fluid that needs to be evacuated. They don't make a big deal of it." Among the Ulithi women of the South Pacific, she says, breastfeeding women join menstruating women in huts, along with their children. "It's kind of a party atmosphere." The huts can be a torturous experience for women in some places, but "there are many other variations on the theme," she says. In some parts of Ghana, West Africa, young girls sit under beautiful, ceremonial umbrellas when they begin menstruating. "The family would give her gifts and pay her homage," says Gottlieb. "She is celebrated like a queen." For the Beng women of Ivory Coast, Gottlieb found that male-imposed restrictions on menstruating women come with a more positive twist. "An older man, a religious leader in the local religion, told me menstruation is like the flower of a tree. You need the flower before the tree can fruit," she says. "That's a very different ideology than the ideology of sin, dirt, pollution.""

- Menstruation

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