Production: Jesús Nicolás
Some authors have proposed that the beard may 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 the jaw, when it was covered by thick hair, versus when it was uncovered.
The researchers covered the epoxy composite with dissected skin segments from domestic sheep, and we used a weight drop impact tester set with a load cell to collect force versus time data. They found that the fully hairy samples were capable of absorbing more energy than the bare or hairless samples. For example, the maximum force was 16% greater and the total energy absorbed was 37% greater in the coat compared to the hairless samples. 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 usually induces the appearance of this secondary sexual character, but not all men produce a beard, and not all do it in the same density.
The presence of the beard has also been explained, on occasions, as an attractive sexual characteristic for females. It is possible that men with more beards reproduced more, and this would lead to genes that stimulate the follicles of facial hair surviving over the hairless ones. There are some observational studies on the power of the attractiveness of the beard in the opposite sex, or on the presence of a 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 blows from enemies.
