Unique among the great apes, human males are able to grow impressive lengths of wiry hair from their jaw, cheeks, and upper lip. Sure, it attracts parasites. Traps food. Interferes with communication, sensation, and perspiration. But they look great… right?

As a hirsute male with a lazy relationship with a razor, I can tell you, beards aren't all they're cracked up to be. But according to a small team of University of Utah biologists, it might at least provide me with a smidgen of protection were someone to punch me in the face.

This isn't an invitation, thank you. But, hypothetically speaking, if such an advantage exists, it might go some way towards explaining why people can grow beards in the first place.

Experimental results suggest the impact force of a blunt strike could be somewhat muted by a thick pelt. Socking actual humans sporting beards could be described as unethical, so biologists Ethan Beseris, Steven Naleway, and David Carrier constructed a fake head to punch instead.

This pseudo lumbersexual was essentially a fibre epoxy 'skull' covered by one of several grades of sheep skin – plucked, trimmed, and full mutton chops. A punch was provided by a falling weight, with the impact on the fake head measured by a load cell.

"We found that fully furred samples were capable of absorbing more energy than plucked and sheared samples," the researchers conclude in their report.

"For example, peak force was 16 percent greater and total energy absorbed was 37 percent greater in the furred compared to the plucked samples."

It's fair to say this all came down to the redistribution of forces provided by the shock-absorbing fibrous fuzz, which in effect slow down an incoming haymaker just enough to potentially save a jaw from a serious fracture.

The researchers view this as evidence of natural selection in favour of growing a beard, pointing out that other animals – like the lion – might also have evolved long hair for protecting their neck and jaw. (Although it's important to note that the case is not so cut and dried when it comes to the purpose of lion manes.)

While it's a fun experiment, there are quite a few knots to comb out of a study like this. Obviously, there is a world of difference between a bearded face and untrimmed sheep skin; they can be compared to an extent, but it would be interesting to have a similar run of trials on something that represents human beards more closely, since the latter can vary quite a bit in density.

Also, while there's no dismissing the seriousness of a jaw fracture, a potentially far more deadly consequence of a punch to the lower skull is the damage caused by rattling the brain around. How a beard affects the overall transfer of energy on a pivoting skull is an open question. 

Carrier intends to look into the effect beards have on the accuracy of a punch. There are also untested possibilities that even a thin bit of facial hair might help a fist slide on by, or reduce the risk of lacerations.

This new study is the latest instalment on a long-standing research interest about human fighting. In 2013, together with his colleague Michael Morgan, Carrier provided experimental evidence to support a proposal that the human hand – at least in part – developed a form of buttressing that improved its performance as an assault weapon.

The following year, the researchers argued the structure of the human face also evolved to withstand a solid hit.

Why the obsession with boxing? There are some reasonable grounds to speculate over the potential for intra-species violence to shape our biology. We are sexually dimorphic, with a clear propensity for male-on-male violence. Unarmed, we also naturally swing our meat hooks at an opponent's face.

Research like this can get us closer to answering the question of how we became naked apes with a penchant for punching, so long as we resist the temptation to accept it as a 'just so' explanation.

The human beard is a puzzle Charles Darwin himself wondered about, concluding they appear to be an ornament to charm or excite the opposite sex. I might be biased, but I think Darwin may have been onto something.

This research was published in Integrative Organismal Biology.