[CURIOSITIES] Why do men have a beard?

YaKuZa--BoSs · June 21, 2020

Facial hair is one of the secondary sexual characteristics of humans. But why is it there?

Some authors have proposed that the beard can function similarly to the long hair of a lion's mane, serving to protect vital areas such as the throat and jaw from lethal attacks. This is consistent with the observation that the jaw, which is superficially covered by the beard, is one of the most commonly fractured facial bones in interpersonal violence. Therefore, it is easy to assume that beards protect the skin and bones of the face when human males fight, by absorbing and dispersing the energy of a forceful impact.

A study has tested the hypothesis that the beard arose to protect the skin and bones of the face, by dispersing the energy of a forceful impact. To do this, they measured the impact force and the energy absorbed by an epoxy resin compound, acting as a jaw, when it was covered by thick hair, versus being exposed.

The researchers covered the epoxy compound with dissected skin segments from domestic sheep, and we used a load cell-fixed weight drop impact tester to collect force versus time data. They found that the completely hairy samples were capable of absorbing more energy than the hairless or bare samples. For example, the maximum force was 16% greater and the total energy absorbed was 37% greater in the coat compared to the samples without hair. These data reinforce the hypothesis that human beards protect vulnerable regions of the facial skeleton from damaging blows.

However, the hormonal pathways that regulate the beard are still a mystery. The follicles that regulate facial hair depend on a multitude of genetic factors that even vary between regions of the planet. Sexual maturity often induces the appearance of this secondary sexual character, but not all men produce beards, and not all do so at the same density.

The presence of the beard has also been explained, on occasions, as an attractive sexual characteristic for females. Men with more beards may reproduce more, leading to genes that stimulate facial hair follicles surviving above hairless ones. There are some observational studies on the power of beard attractiveness in the opposite sex, or on the presence of beard as an indicator of status, but without clear conclusions. On the other hand, the assumption that the beard has a role in sexual competition is not incompatible with the explanation that the beard is there to cushion the blows of the enemies.

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