The Evolutionary Anomaly of Modern Menstruation and Associated Health Risks

Key Insight

Evolutionary research by Beverly Strassmann on the Dogon tribe in Mali revealed a stark contrast in reproductive patterns compared to contemporary Western women, highlighting that what is now considered normal for menstruation is evolutionarily abnormal. Dogon women, living without contraception, typically experience menarche at 16, give birth 8 or 9 times, and average only about 100 menstrual periods in their entire lives, largely due to prolonged periods of pregnancy and breastfeeding that suppress ovulation for an average of 20 months at a time. This sharply contrasts with Western women who average 350 to 400 lifetime menses, a significant shift over the last century.

This 'incessant ovulation' in modern women is increasingly recognized by evolutionary medicine as a serious health problem, as women's bodies are subjected to stresses not accounted for by evolution. Beyond common discomforts like abdominal pain, mood shifts, migraines, endometriosis, fibroids, and anemia (one of the world's most serious health problems), frequent menstruation significantly increases the risk of certain cancers. Each ovulation involves an egg bursting through the ovarian wall, requiring cell division to heal, and these divisions can lead to cancerous errors; consequently, each pregnancy and associated breastfeeding period, which prevents ovulation for about 12 months, reduces ovarian cancer risk by 10%.

Similarly, endometrial cancer risk rises with menstruation, as estrogen stimulates the growth of the uterine lining, prompting potentially dangerous cell division. The conventional birth control Pill, by suppressing ovulation and countering estrogen surges, effectively mitigates these risks, functioning as a protective agent for the reproductive system. Taking the Pill for ten years can reduce ovarian-cancer risk by approximately 70% and endometrial-cancer risk by around 60%. This beneficial effect demonstrates the Pill's true 'natural' impact in an evolutionary sense: it rescues the ovaries and endometrium from the unprecedented demands of modernity rather than merely mimicking natural cycles.