Female Disgust May Have Caused Humans to Evolve Less Hair to Avoid Disease-Carrying Parasites

Researchers have found new evidence to suggest that female disgust caused humans to evolve less hair. Women who rated themselves higher on measures of disgust appeared to prefer pictures of clean-shaven men, as revealed by a study published in Royal Society Publishing.

Researchers asked women to rate the attractiveness of 30 male faces for long-term and short-term relationships, as well as how disgusted they were by images of parasites.

They found that those who reported higher levels of disgust tended to prefer the clean-shaven faces, but women in general displayed a preference for men with facial hair—particularly when they were judging potential suitors for long-term relationships.

The results add more weight to the "ectoparasite avoidance hypothesis"—the idea that our early human ancestors lost body hair as women avoided excessively hairy men, thereby reducing the risk of contracting disease-carrying ectoparasites (parasites like fleas and ticks that live outside the host). This suggests that sexual selection causes humans to become less hairy as time goes on.

The study's authors say that this is the first evidence in support of the hypothesis, but are wary of drawing too many conclusions before other studies can back up their research.

They point out other factors (social, economic and ecological) that can just as easily, and perhaps more so, affect a person's choice of facial hair, including fashion.

The researchers also caution that the study was conducted on U.S. women only and, therefore, may not reflect choices in other societies. Previous analyses of facial hair fashions suggested the number of men sporting facial hair is higher in cities with larger populations and higher life expectancies, but strongest in countries with lower average incomes.

Previous studies have almost overwhelmingly shown that women prefer men with facial hair, with heavy stubble often coming up on top. This appears to be especially true for long-term relationships. According to one study, it might be because women find men with facial hair more masculine, confident, industrious, generous and sincere.

Jason Momoa
Jason Momoa arrives for the World Premiere Of Apple TV+'s "See" held at Fox Village Theater on October 21, 2019 in Los Angeles, California. New research suggests women display a preference for beards, but women who rated themselves higher on measures of disgust appeared to prefer pictures of clean-shaven men. Albert L. Ortega/Getty

Other studies have suggested our attitude to disgust can affect our politics.

In one instance, scientists could identify a conservative from a liberal from brain scans when they were shown disgust-provoking images—so much so that a single image was enough to predict a person's political affiliation. In another, people with less tolerance for body odor were found to more likely to hold authoritarian beliefs.