Sex hormones control the monthly cycle of the woman and ensure her fertility – and they provide a fragrant body odor. As researchers from the University of Bern now show, some women smell better in the nose of men than others. Namely those who are most suitable for reproduction.
Not only do we trust our eyes, but we also follow our nose: when choosing a partner not only the visual impression, but also the smell plays an important role, both in the animal kingdom and in humans. Previous studies have shown that women, according to their monthly cycle, at different times smell differently to men: the most attractive smell of a woman in the male nose during the most fertile days of her cycle – the time she can actually reproduce. What has not been answered before: is there a difference between the individual smells of women, do certain women smell "better" than others?
Now a research team led by Daria Knoch from the Department of Social Psychology and Social Neurosciences at the University of Bern in collaboration with colleagues from the University of Constance, the Economic Institute of Thurgau and the Inselspital, University Hospital Bern, is showing that this is really the case: the smell of certain women is universally better for Men than others. The researchers also discovered the reason for this: the female sex hormones estrogen and progesterone are responsible for the "fragile" choice of men.
Certain sex hormones make the woman's scent attractive
Depending on the level of sex hormones, women are found more attractive by men or less: "Women with high estrogen and low progesterone levels are the most olfactorily the most attractive for men," says Daria Knoch, who summarizes the results of the study. What makes sense for the researcher from an evolutionary biological point of view: these hormone levels – much estrogen, little progesterone – indicate high female fertility. According to the theory of evolution, men search for women, with which they can multiply as well as possible.
The researchers also investigated other factors that can influence the smell: the stress hormone cortisol and certain genes that form the immune system. "Some studies state that the choice of a partner is based on the widest possible immune system of men and women, so that the offspring get an equally good immune system against pathogens in the cradle", says Janek Lobmaier, first author of the department of Social Psychology and Social Sciences. Sciences. neuroscience. However, the results clearly show that these two factors do not affect the attractiveness of the female odor.
Strict test protocol
The researchers conducted their research with 28 women and 57 men. The women who gave their scent followed "a strict protocol to minimize all factors that could upset the smell," Lobmaier said. The women were therefore not allowed to prevent contraception by means of a "pill", did not share their bed with anyone during the period of smell, they washed themselves with neutral shower material, drank no alcohol on these days and did not eat any spiced food. At the time of highest fertility, they used cotton blocks in the armpits to "catch" their own individual scent. Saliva samples were used to determine their hormone levels. Later in the lab, the men sniffed the cotton pads and distributed 0 to 100 points for each smell they observed – with the familiar result.
Signals of the woman
"Reproductive hormones are indications of the fertility of women, and the higher their level, the more attractive the woman is for men," says Lobmaier. For example, estrogen also has a positive effect on the visual female attraction, as studies have shown: high levels of estrogen make the face and body of the woman attractive to men. And also their smell – at least in women who do not use hormonal medicines. How it relates to the pill was not investigated: "But it is likely that hormonal contraception will distort the body's own odor," Knoch said. The research is now published in the journal "Proceedings of the Royal Society B".
Source: University of Bern
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