Humans are not nearly as furry as our closest primate relatives, a fact that has puzzled evolutionary biologists for more than a century. One common theory for our relative hairlessness suggests that women long ago adopted a preference for less hairy guys as a way to avoid lice and other nasty bloodsuckers that might call a pelt home.

But new research suggests that this so-called “ectoparasite avoidance hypothesis” may not explain the evolution of human hairlessness. In fact, women prefer relatively hair-free guys across the board, according to new research published online Sept. 13 in the journal Archives of Sexual Behavior. This preference for smooth skin holds whether or not parasite risk is high. …

Instead, the researchers found that very few women in either country prefer a hairy chest. Only about 20 percent of women rated the more hirsute versions of the men as more attractive.