
There have long been theories that women’s menstrual cycles align with the moon, and now a new study suggests there’s some truth to that. Using years of records kept by 22 women, researchers found that for many, menstrual cycles “intermittently” synced up with the phases of the moon. The link happened only about one-quarter of the time for women aged 35 or younger, and just 9% of the time for older women. There was a great deal of variance, though, among individuals. And for a few women, there were hints that excessive exposure to artificial light at night could have thrown off any moon-menstruation synchrony. One expert called the findings “interesting,” and said they might reflect remnants of a lunar influence that benefited humans’ ancient ancestors. Early primates were nocturnal creatures, so a degree of moon-influenced behavior would make sense for them, according to Deena Emera. Emera, who was not involved in the study, is an evolutionary geneticist based at the Buck Institute’s Center for Reproductive Longevity and Equality, in California. Mating is risky business, Emera noted, as it makes animals vulnerable to predators. So mating during the new moon, under cover of more darkness, would be a “reasonable strategy,” she said. That also means there would be an advantage to ovulation being timed to the new moon. “I think any [moon-menstruation] synchronization seen today… read on > read on >