Can you imagine picking your soul mate merely by their scent? It has been shown that people can show a preference to certain people of the opposite sex based on how they smell (Wedekind et al 1995; click on photo for another such study). In the experiment, participants were asked to wear a t-shirt for two consecutive nights, and remain as odor-neutral as possible during this period (use fragrance-free detergent and soap, refrain from exercising and eating smelly foods). Participants also had their MHC (major histocompatibility complex) typed. The shirts were then collected and given to members of the opposite sex to sniff and rate how pleasant the odors were to them. The more pleasant the odor, the “sexier” that person was considered. These results were compared to the degree of closeness of the male’s and female’s MHC. The males and females that had more difference between their MHCs found each other’s scents more attractive than those who had similar MHCs. Essentially, people’s preference towards different MHCs ensures a greater chance for variation in this important factor of the immune system. This is an important selection aid to avoid inbreeding. By nature, people tend to show preferences towards people that are more like them. If there were not selection guides, like the scent preference linked to MHCs, there would be a much higher incidence of inbreeding. As a result, there would be less genetic variation and a higher incidence of accumulation of deleterious mutations or rare genetic diseases in the inbred population.
A more recent study showed human males’ innate ability to detect higher probability for mating success at strip clubs (Miller et al 2007).
Lap dancers were asked to report their tip earning for each shift they worked, and to also record their ovulatory cycle for 60 days. The results showed that men were most responsive to women approximately one week after their menstruation had ceased. This implies that the men found the women most attractive (indicated by a higher tip amount) when they were the most fertile—just before ovulation. Part of this study also asked men to rate the attractiveness of each woman’s body (the faces were covered) in photographs of women during their peak fertile period compared to other times during their cycle. The picture taken during ovulation was deemed the most attractive. This is due to the slight physical changes in women during ovulation: increased facial attractiveness, decreased hip-to-waist ratio, and increased body symmetry—all traits that men perceive as more attractive in a woman. This heightened sensitivity to women’s ovulatory cycle is comparable to other animals—such as dogs—being in estrous or “heat”.
Wedekind, C., Seebeck, T., Bettens, F., Paepke, A.J. (1995). MHC-Dependent Mate Preferences in Humans. Proceedings of the Royal Society B: Biological Sciences, 260(1359), 245-249. DOI: 10.1098/rspb.1995.0087
Miller, G., Tybur, J., Jordan, B. (2007). Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrus? Evolution and Human Behavior, 28(6), 375-381. DOI: 10.1016/j.evolhumbehav.2007.06.002