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.

–Barbara Berr, via the Internet

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?”

Then again, who knows? People have figured there was a connection between the lunar month and menstruation for as long as women have been getting the month-lies. Moon, month, and menstruation are all related etymologically. No less an authority than Charles Darwin believed that menstruation was linked to the moon’s influence on tidal rhythms, a legacy of our origin in the sea. The coincidence between the lunar and menstrual cycles is closer than George Abell would have us believe–studies have found the average menstrual period is 29 days and change. At least some critters’ biologies are linked to the lunar cycle; in the lemur, for example, estrus and sex tend to occur around the time of the full moon.

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.


Back to Barry Popik. Barry, you’ll remember from last week’s column, is the amateur word researcher who established that New York’s nickname “the Big Apple” was initially popularized by horse-racing writer John J. Fitz Gerald in the 1920s rather than by jazz musicians as was once believed.

Next Barry turned his attention to Chicago’s nickname, “the Windy City.” Common folk believe Chicago was so dubbed because it’s windy, meteorologically speaking. The more sophisticated set (including, till recently, your columnist) thinks the term originated in a comment by Charles Dana, editor of the New York Sun in the 1890s. Annoyed by the vocal (and ultimately successful) efforts of Chicago civic leaders to land the world’s fair celebrating Columbus’s discovery of America, Dana urged his readers to ignore “the nonsensical claims of that windy city”–windy meaning excessively talkative.

But that may not be the true explanation either. Scouring the magazines and newspapers of the day, Popik found that the nickname commonly used for Chicago switched from the Garden City to the Windy City in 1886, several years be-

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?

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.