The human sense of smell may be regarded as poor in comparison with other animals. A dog for example, has around two hundred million receptors as opposed to the five or six million available to Homo sapiens.
However smell is still an important ingredient in the hierarchy of attractiveness and even in the potential choice of a partner.
The T-shirt Test
Claud Wedekind, a biologist at the University of Lausanne, gave new T-shirts to 44 men and instructed them to wear the clothing for two nights. Scent-free soap and aftershave ensured the T-shirts remained free from individual odour.
After being worn for two nights, the T-shirts were sniffed by 49 women and rated for levels of attractiveness. A higher number than would be expected by chance preferred the odour of T-shirts worn by men immunologically different to them. Why was this?
MHC Influences Who You Date
The difference was in the Major Histocompatibility Complex (MHC), a sequence of approximately 100 immune system genes coded for proteins that assist the immune system in recognising pathogens.
The scent of the preferred shirts also reminded the women of past or present partners, an indication that MHC has an influence in the world of dating.
Partners whose immune systems are different produce children that are more resistant to disease, the variety of genes present helping to protect against a number of pathogens and toxins.
The Scent of Desire
Rachel Herz, author of The Scent of Desire, points out that MHC profiles are as individual as fingerprints. The plethora of available combinations means one person's attraction may be another's repulsion and there can be no universally preferred combination.
“Body odour is an external manifestation of the immune system, and the smells we think are attractive come from the people who are most biologically compatible with us.”
She continues, “Interestingly, one of the most common things women tell marriage counsellors is ‘I can’t stand his smell’.”
The Effect of the Contraceptive Pill
Wedekind discovered one exception to the rule that women show a preference for the scent of men with different MHC profiles. This was in the case of women taking the contraceptive pill.
In the study, women on birth control pills showed preference for the T-shirts worn by men with similar MHC profiles to their own – the opposite reaction to their contraceptive free co-testers.
Rachel Herz feels this may be an effect of the pill on the body’s mechanisms as its tricks the body into feeling it is pregnant. As pregnancy is a vulnerable state, it appears to foster a preference for genetically similar kin, as these are likely to be seen as protectors.
Could this cause potential difficulty in the choice of long-term partners?
Hertz says, “It is like choosing a cousin as a marriage partner. It constitutes a biological error. If you are looking for a man to be the father of your child, go off the pill before you start your search.”
However, the situation becomes more complicated if the woman was taking the pill when she met her partner. Hertz feels that once a relationship has moved to long-term commitment, smell and emotion become co-existent.
“If she’s in love, he could smell like a garbage can and she would still be in love with him.”
Scent and Attraction
Though scent can play an important, often subliminal, role in attractiveness, there are of course still many other relevant factors in the choice of a potential partner.
MHC incompatibility may have its place, but shared hobbies, common interests, physical preference and intelligence will always prove major contributory factors.
Related Article
References
The Scent of Desire by Rachel Herz (William Morrow – October 2007)
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