Science + Technology

Near Ovulation, Your Cheatin' Heart Will Tell on You, Find UCLA, University of New Mexico Researchers

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Higgamous hoggamous,woman's monogamous; hoggamous higgamous, men are polygamous. Or maybe not.

New research from UCLA and the University of New Mexicosuggests that members of "the gentler sex" may have evolved to cheat on theirmates during the most fertile part of their cycle — but only when those matesare less sexually attractive than other men.

"Women know they have attractions that come and go, but theyprobably don't realize that these urges are tied to their cycle — as well asour evolutionary past," said Martie G. Haselton, a UCLA researcher and authorof two new studies on the subject. "They just know that suddenly one daythey're attracted to their hunky neighbor or handsome co-worker."

Men, meanwhile, seem to be aware on some level of this possibilityand appear to step up mate-guarding strategies when their wives or girlfriendsovulate, even when neither is keeping track of the woman's cycle, the researchshows.

"It's not just that men are more jealous and possessive whentheir partners ovulate, but they're also more attentive to their partners andmore giving to their needs," said collaborator Steven W. Gangestad, aUniversity of New Mexico psychologist.

"Although men are probably not aware of it, they behave asthough they're genuinely concerned about being cuckolded," Gangestad continued."It turns out that there's some basis for the fear."

The findings advance recent research by Gangestad that hassuggested a proclivity toward infidelity during ovulation. The new research,generated in collaboration with UCLA's Center on Behavior, Evolution, andCulture, pinpoints women who may be at greatest risk. The findings also suggestan evolutionary explanation for the so-called "adaptation."

For the first study, which will be reported in the Jan. 4 scholarly journal "Hormones andBehavior," Haselton, an assistant professor of communication studies andpsychology at UCLA, and Gangestad recruited 38 female coeds from a large U.S.university. (The researchers are declining to name the institution so that thesubjects don't find themselves in the position of being grilled by mates wholearn of the sensitive findings.)

The subjects were asked to reveal information from whichtheir date of ovulation could be deduced. Then they were asked to rate their partner'ssexual attractiveness as measured by his desirability for a fling as well ashis suitability as a long-term mate, on the theory that the first would revealhis sexual attractiveness while the second would reveal his abilities as aprovider or potential provider.

Finally, the subjects submitted 35 diary-like entries,rating the strength of their attractions that day to men other than their matesand the frequency and manner with which they flirted or otherwise acted outthose attractions. Also on a daily basis, the co-eds rated their own sexualattractiveness, sexual desires and sense of power within their romanticrelationships.

Analyzing the diaries, Haselton and Gangestad found thatovulating had a strong effect on all women. Regardless of where they stood onother measures, the co-eds felt more desirable, attractive and powerful intheir relationships during the mid-point of their cycle. But women who ratedtheir mates as more suitable for long-term involvement than a quick fling haddifferent behavior and desires than women who considered their mates hot.

"When women were mated to men with low sexual versusinvestment attractiveness, they were particularly likely to experienceincreased attraction to men other than their partners at mid‑cycle,"Haselton said.

The mates of these women, meanwhile, appeared to appreciateunconsciously what they were up against. Their wives and girlfriends reportedmany more acts of mate-guarding behavior than women who considered their matesto be fling-worthy.

"What is at stake is not just the loss of face or the lossof love," Haselton said. "This is about Darwinian prosperity. Males who did notsuccessfully guard their mates are not our ancestors."

Only one group of men diverged from this pattern: They werethe ones whose wives and girlfriends were the most physically attractive.

"These guys used mate-guarding tactics all the time —whether the woman was ovulating or not," Gangestad said. "If their wives andgirlfriends were correct, these guys behave as though they expected the womento be snatched from them at any point."

For the second study, Haselton andElizabeth Pillsworth, a UCLA graduate student, recruited 43 normally ovulatingwomen, who similarly rated their partner's sexual attractiveness. They also reported their own desires andtheir partner's mate retention behaviors at high and low fertility. But thesesubjects did so on just two occasions — once on a day near ovulation and oncein the non-fertile days following ovulation — not on a daily basis. And thesubject's cycle was not a matter of deduction. Lab tests for a hormone surgethat marks ovulation (luteinizing hormone) confirmed that women were indeedfertile in one of the reporting sessions. The researchers then looked forpatterns in the women's responses.

The findings, which are forthcoming in "Evolution and HumanBehavior," the flagship journal of the field of evolutionary psychology, confirm the first study: Near ovulation, these womenalso were more likely to fantasize about men other than their mates, but onlywhen they didn't consider their mates to be particularly sexy.

Together the studies give a sense of the extent to whichhuman evolutionary history may still play a role in the present.

"Since our female ancestors couldn't peer into a potentialpartner's genetic makeup, they had to base their decisions on physicalmanifestations of the presence of good genes and the absence of geneticmutations, which include masculine features such as a deep voice, muscularbody, dominant behavior and sexy looks," Haselton said. "So we still feel drawnto these visible markers for what at least in the past proved to be indicatorsof good genes. Ancestral women who were attracted to these features producedoffspring who were more successful in attracting mates and producing progeny.The legacy of the past is desire in the present."

But as any mother with mounting bills and laundry canattest, women do not look only for good genes in a potential partner.

"In the reproductive arena, women want men to contributeboth quality care and good genes," Haselton said. "The problem is that therearen't many potential mates who are high in both. So many women are forced tomake trade-offs."

Numerous studies have found a pronounced preference on thepart of women for a kind and resourceful investing partner. Temptation appearsto raise its head when the mate is not attractive as well.

"What we find attractive is no accident," Haselton said."We've evolved to value indicators of biological fitness."

The findings contradict long-held views in biologicalevolution about the types of mates that women find attractive and how thoseattractions differ from the ones experienced by men.

"According to the traditional evolution story, men valueattractiveness in a mate, whereas women value resources and status," Haseltonsaid. "But the story appears to be much more nuanced. Physical attractivenessis very important to women, but to see this you have to catch women during thenarrow window of fertility within the cycle."

These phenomena also help explain at least some of thestoried tension between the sexes.

"From an evolutionary perspective, what's in the bestinterests of a woman and her partner can be fundamentally different," Haseltonsaid. "It may well be in her evolutionary interest to chose a different geneticpartner for her offspring. What is in the male's interest is not to let thishappen, ever. It's a huge evolutionary cost because he spends time and energyensuring the survival of genes that aren't his own. So he has an opposingstrategy: He's possessive and jealous."

But in an era when birth control plays a prominent role indetermining the amount of genetic material that any one couple passes on to thenext generation, these adaptive traits may no longer serve their evolvedfunction.

"The temptation to cheat on one's mate may be no differentfrom hankering for a Krispy Kreme donut and other fatty foods," Haselton said."It is an appetite that apparently helped ancestral humans to transmit theirgenes to subsequent generations, but today it may only get us into trouble."

-UCLA-

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