Evolutionary psychologists tell us that one of the reasons why women find masculinity attractive is that high testosterone is a sign of a strong immune system. A strong immune system, in turn, in a sign of good genes and childhood development (testosterone is an immunosuppressant and only men with good genes can overcome its drawbacks). These strong square-jawed macho men aren’t necessarily good dads: they’re more likely to be uncooperative, combative, and aggressive. But they may offer good genetic material for your kids, depending on the circumstances.

So how do you prove that women equate masculinity with good genes and healthy immune systems (subconsciously, at least)? An indirect approach was taken by Lisa DeBruine and her colleagues at the Face Research Lab at the University of Aberdeen. (The Lab conducts many fascinating studies on attraction, some of which I reference in BLONDES.)

In this new study, DeBruine recruited 345 women of all ages to rate faces. The faces were digitally altered, and ranged from very masculine to very feminine. Participants also completed a test called the Three-Domain Disgust scale, designed to measure moral disgust (deceiving a friend), sexual disgust (hearing strangers have sex), and pathogen disgust (stepping on poop).

Turns out that women’s preference for masculinity in male faces was correlated with disgust sensitivity to pathogens, but not in the moral and sexual domains. (Yes, hypochondriacs do prefer macho men!) DeBruine speculates that in certain situations, such as disease-ridden environments, women are wired to prefer high-testosterone males. The benefits of their good immune system genes are worth the tradeoff.

The testosterone-means-good-genes theory, anyway, may explain why women in disease-ridden environments are likelier to choose macho guys. Explains DeBruine et al.:

Because a partner’s heritable health is of greater value when pathogens are a greater concern, concern about pathogens is likely to also be a factor that contributes to the resolution of this tradeoff. Cross-cultural differences in mate preferences and mating systems vary consistently with differences in pathogen prevalence. When people from 29 different cultures were asked to rank a series of attributes based on how important they would be in a mate, people in areas with a high prevalence of pathogens ranked physical attractiveness higher than people in areas with a relatively low prevalence of pathogens did. Also consistent with these

findings, rural Jamaican women prefer masculinity more than British women do…

So do hypochondriacs, fearful of disease, marry more macho men (e.g. self-professed hypochondriac Susie Essman and her new husband?) As environments become more sterile, will we prefer men with softer, sweeter faces and personalities? Or will the next swine flu outbreak inspire us to pursue pigs?