Males begin growing facial hair during puberty when they start reaching sexual maturity. During that tumultuous time, boys get taller and their voices get deeper. That's because male hormones, particularly testosterone, go into overdrive. While it's easy to understand growth spurts and deep voices, what's the purpose of facial hair? It's not necessary for our survival. Nor does it play a direct role in reproduction. It doesn't even keep you warm in frigid climes.
The answer seemingly lies in evolution. Some experts believe that facial hair allows males to attract mates. In their opinion, women often base their perceptions of a man's age, social status and vitality on the color and texture of his beard. If she likes what she sees, the species propagates [source: Cornell Center for Materials Research].
A 2012 study published in the journal of Behavioral Ecology flies in the face of this common evolutionary theory. Researchers at Victoria University in Wellington, New Zealand, and at the University of Lethbridge in Alberta, Canada, showed a group of women in Samoa and New Zealand pictures of men. Some had beards; others did not. The majority of women did not think bearded men were any more attractive than men without beards [source: Alexander].
If it's not about sexual signals between men and women, then what is it? In the same study, researchers concluded that bearded men might intimidate their rivals. A thick, bushy beard, for instance, may make a man look larger and more menacing, and in an evolutionary context, that might work well in scaring off a potential mate's suitors or in a battle over other resources [source: Alexander].
Both the men and women in the study saw bearded men as more aggressive, especially when that person had an angry look on his face. "Facial hair may intimidate rival males by increasing perceptions of the size of the jaw, overall length of the face, and by enhancing aggressive and threatening jaw-thrusting behaviors," the researchers said. Moreover, other studies suggest juries are more likely to find a bearded man guilty of a serious crime [source: Alexander].
The bottom line: If you want to woo a girl, shave. If you want to intimidate someone, grow a beard. In 2013, several members of the Boston Red Sox grew beards to inspire bristly camaraderie and to intimidate their opponents. They won the World Series. While some baseball fans loved the beards, the whiskers engendered a primal response in many people, especially New York Yankee fans. "I never hated the Red Sox more," one New York fan wrote on a blog. "And I might add their beards are making me sick!"