The widespread belief that men are more attracted to the scent of a woman when she is at her most fertile may not be true after all, say researchers.
A flurry of studies in recent decades has made a compelling case that female body odor changes over the menstrual cycle, allowing perceptive males—in theory, at least—to see when mating is most likely to lead to pregnancy.
But researchers in Germany who had men sniff women’s body odor found no compelling evidence that it was more attractive when the women were at their most fertile. And they saw no variations in the smell’s chemical composition associated with peak fertility.
The findings suggest that if body odor does correlate with female fertility, it may not be obvious, at least when you first meet a woman. The researchers do not rule out the possibility that men can sense changes in female body odor when they spend a lot of time with the same woman.
“I see this as a starting point to reevaluate the field,” said Madita Zetzsche, a graduate student at the University of Leipzig and first author of the study. “We don’t dominate the previous studies, but we need to look at this again with the more robust techniques we have now.”
Zetzsche and her colleagues decided to investigate the question when they couldn’t find previous studies showing that fertility caused chemical changes in female body odor. “It would be essential to see an effect,” Zetzsche said.
They recruited 29 non-smoking heterosexual women aged 20 to 30 years, none of whom were using hormonal contraception. The researchers then collected samples of the women’s armpit odor over 10 sessions before, during and after their fertile period. Ovulation test strips and levels of the hormones estradiol and progesterone in saliva were used to confirm the women’s cycle.
Write in Proceedings of the Royal Society Bthe team describes how they found no significant differences in the chemical composition of body odor when they compared samples taken on women’s fertile and non-fertile days.
In the next part of the study, the researchers asked the women to stick cotton pads on the skin under their armpits and wear them for 12 hours overnight. They then invited 91 men aged 19 to 40 to rate the women’s scents, taken at different stages of the menstrual cycle. Neither man sniffed the same woman twice.
Again, there was no compelling relationship between the men’s odor ratings and the women’s fertility, suggesting that if fertile women smell differently, the effect may be too subtle for men to pick up on the first time they meet a woman. track.
The work comes after several studies made the case for body odor reflecting female fertility. More than a decade ago, researchers at the University of California at Los Angeles reported that men were more attracted to women’s body odor when they were fertile, which makes the scientists wonder if the smell of a woman can influence men’s sexual approaches. In 2018, a team led by Daria Knoch, a professor of social neuroscience at the University of Bern, showed that levels of reproductive hormones explain individual differences in women’s body odor.
Knoch said the latest study was “interesting” but “surprising” from an evolutionary perspective. “I wonder how the results would have turned out if the authors had controlled for a very important factor that influences body odor preferences: the major histocompatibility complex, or MHC,” she said. “MHC genes influence the production of molecules in sweat and body fluids, which contribute to a person’s unique scent. Some studies have suggested that men prefer body odors from MHC-dissimilar women.
