What’s the connection between the human menstrual cycle and the moon? Do our cycles last exactly one lunar month for a reason, or is it just a coincidence? I wonder how our cycles–not to mention our calendars–would work if we didn’t have a moon.
Best of Chicago voting is live now. Vote for your favorites »
The smart money says it’s coincidence. In Science and the Paranormal (1983), astronomer George O. Abell writes, “The moon’s cycle of phases is 29.53 days, while the human female menstrual cycle averages 28 days (although it varies among women and from time to time with individual women); this is hardly even a good coincidence! The corresponding estrus cycles of some other mammals are 28 days for opossums, 11 days for guinea pigs, 16 to 17 days for sheep, 20 to 22 days for sows, 21 days for cows and mares, 24 to 26 days for macaque monkeys, 37 days for chimpanzees, and only 5 days for rats and mice. One could argue, I suppose, that the human female, being more intelligent and perhaps aware of her environment, adapted to a cycle close to that of the moon, while lower ani-mals did not. But then the 28-day period for the opossum must be a coincidence, and if it is a coincidence for opossums, why not for humans?”
Efforts to turn up similar patterns in humans have had unimpressive results, however. Several researchers over the years have claimed to detect lunar rhythms in menstrual onset and such; others see nothing. Biologist Winnifred Cutler, in a 1980 paper, found that 40 percent of women in a random sample showed “a preponderance of menses onsets in the light half-cycle of the month” (the two weeks centered on the full moon). To me this suggests 60 percent of women didn’t show any coincidence, but Cutler says that’s because I just don’t get it, honey. Maybe not, but if there really is a moon-menstruation link, you couldn’t prove it by me.
fore Dana’s comment. The earliest citation was from the Louisville Courier-Journal in early January 1886, when it was used in reference to the wind off Lake Michigan. In other words, the common folk have been right all along! However, when Popik attempted to notify former Chicagoan and soon-to-be New Yorker Hillary Rodham Clinton of his findings, she blew him off with a form letter–and this on an issue she could have ridden into the Senate. Come on, Hill, quit worrying about the Puerto Ricans and pay attention here. You want to lose the etymologist vote?
