Booty Call: How to Spot a Fertile Woman

LiveScience

By Stephanie Pappas, LiveScience Senior Writer

posted: 17 October 2010 08:43 am ET

Ask the average person how the menstrual cycle affects women’s moods, and you’re likely to get an earful about PMS, or premenstrual syndrome. While it’s true that PMS symptoms are common (although not as stereotypical as usually believed), new research is finding women’s behavior shifts at another point in the reproductive cycle: ovulation.

Two new studies in the November issue of the journal Evolution and Human Behavior find that women get a little wilder during their most fertile days of the month. One study found that fertile women are more open to the idea of hooking up with a stranger or acquaintance, while the second found that women with less masculine-looking partners are more likely to lust after strong-jawed men during fertile days than women with partners with manly mugs.

The new studies are two of more than 20 that have examined the effects of ovulation on the way women dress, talk and think. While it’s not yet clear if or how these temporary changes affect women’s relationships in the real world, they may by a key to humanity’s past.

“The idea is you see the preferences that would have evolved ancestrally still show up,” Steven Gangestad, a University of New Mexico evolutionary psychologist and co-author on both new papers, told LiveScience.

Ovulation and lust

Until about a decade ago, most research on the menstrual cycle focused on PMS, which occurs after ovulation and before menstruation. Few people had investigated whether ovulation affected women, Martie Haselton, a psychology professor at the University of California, Los Angeles, told LiveScience. (Ovulation occurs when a woman’s body releases an egg down the fallopian tube where it can meet up with Mr. Sperm.)

“Nobody was asking what happens on fertile or non-fertile days,” Haselton said.

One reason no one had tackled the question is that researchers in human evolution had long assumed that ovulation didn’t matter much in humans. Unlike other mammals, which go into “heat” during fertile periods, women can be up for sex any time of the month. Evolutionary theorists have tried at several explanations for the loss of this estrus cycle in humans, one of the most common being that humans lost the “heat” phase to conceal ovulation. If a man didn’t know which sexual encounter would pass his genes along, the theory went, he’d be more likely to stick around and help raise offspring.

The problem is that men do seem to be able to tell when their partner is ovulating, albeit imperfectly. No one knows how men can tell (smell is one hypothesis), but several studies have found women report that men become more attentive and jealous around fertile days. One 2006 study published in Evolution and Human Behavior found that when women were fertile, their male partners saw other men as a greater threat to their dominance.

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Author: Leslie Carol Botha

Author, publisher, radio talk show host and internationally recognized expert on women's hormone cycles. Social/political activist on Gardasil the HPV vaccine for adolescent girls. Co-author of "Understanding Your Mood, Mind and Hormone Cycle." Honorary advisory board member for the Foundation for the Study of Cycles and member of the Society for Menstrual Cycle Research.