Beard growth explained by the need to soften blows to the face

(ORDO NEWS) — The long vegetation covering the lower part of the male face is one of the most striking signs of sexual dimorphism among people. Mustache and beard are not very comfortable: food gets stuck in them and parasites settle in, hair makes sweating and facial communications difficult.

Despite this, they remain attractive and can be preserved as a result of sexual selection, like a tail in male peacocks or a horn in narwhals. But maybe there is some practical meaning in the beard?

In fact, there is a “fist hypothesis” that explains some features of the anatomy of the human hand and face by the need to strike and take blows. And recently, its author – David Carrier from the University of Utah – tried to connect facial hair with this, suggesting that a beard can serve to soften the opponent’s blows. Carrier and his colleagues write about this in an article published in the journal Integrative Organismal Biology.

There is a certain logic in this, and the authors name three key points in support of their idea. Firstly, the vast majority of acts of aggression in representatives of our species are associated with male conflicts. Secondly, until recently, direct fist fights remained the dominant form of such conflicts.

Thirdly, evolution was supposed to contribute to the development of phenotypes that help to win in these fights.

To test their idea, scientists conducted an experiment with a model of a human skull made of epoxy resin, covering it with sheep skin with wool of varying degrees of haircut or not at all trimmed. Accurately measured blows were inflicted by a falling load, and the load sensor recorded the damage received. As might be expected, unshaved wool absorbed more energy than shaved and shaved varieties (sometimes up to 37 percent more).

According to the authors, this confirms their initial hypothesis, especially since such a function of the hair is very widespread. Even a luxurious mane of lions is believed to help protect the muzzle and throat. Nevertheless, it is still too early to finally accept their conclusions – it was not without reason that Darwin explained facial hair to the usual sexual selection.

It is worth noting that, firstly, the fleece is much thicker and denser than human hair and, accordingly, is able to absorb more shock energy. Secondly, such an absorption can reduce the risk of a direct bone fracture, but it is unlikely to protect the brain from an equally dangerous concussion. Loud statements need particularly reliable evidence, and Carrier has yet to definitively substantiate the “fist hypothesis” – or abandon it.


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