Sporting a “millennial beard” is a fashion statement for many.
Scientists from the University of Utah have discovered, however, men may have evolved facial hair for a rather more practical reason.
Beards cover the lower jaw, one of the most commonly broken bones during a fist fight.
Using sheepskin to mimic a beard, the scientists found facial hair appears to “absorb” the energy of a blunt force.
Although the reason for this is unclear, it is thought to be due to beards reducing the friction between the jaw and the object striking it.
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Beards have been described as a sign of masculinity and “social dominance”, suggesting they play a role in “male contest competition” for a partner.
Some experts have claimed beards may play a similar role to a lion’s mane, which is thought to protect its jaw and throat from attacks.
Charles Darwin, the “father of evolution”, agreed with this theory, but suggested beards in men may be an “ornament” that attracts female attention.
As with other great apes, most fights occur between men, with the face usually being the target.
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To test this theory, the scientists used a piece of carbon fibre to mimic how bone absorbs and disperses “impact force”.
Using sheepskin, the fibre was covered with thick hair or skin that had been sheared or plucked.
The scientists noted it was “not practical to obtain fully bearded skin samples from human cadavers”.
During the experiment, a “weight impact tester” measured the force of a blow.
Results, published in the journal Integrative Organismal Biology, reveal the “fully furred samples” absorbed on average nearly 30% more energy than the sheared or plucked “bone”.
No significant difference was found between the sheared and plucked samples.
“The results of this study indicate that hair is indeed capable of significantly reducing the force of impact from a blunt strike and absorbing energy,” wrote the scientists.
“If the same is true for human facial hair, then having a full beard may help protect vulnerable regions of the facial skeleton from damaging strikes, such as the jaw.”
Beards may equally protect against cuts and other injuries, they added.
The “protective nature” of beards may give men a competitive edge, which could explain why facial hair is linked to “high masculinity, social dominance and behavioural aggressiveness”.
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The scientists wondered whether hair fibres “take up the force of the load” hitting the skin.
“This is a similar mechanism to how a Kevlar fibre vest distributes the force of an incoming bullet,” they wrote.
The scientists stressed their results “provide no evidence that beards provide protection against being knocked out”.
Beards also vary around the world, with men of “Middle Eastern and northern European ancestry capable of growing thick, bushy beards, whereas people of east Asian and American Indian heritage have relatively little facial hair”.
It is unclear why beards differ between populations.
The scientists wondered whether ethnic backgrounds without beards get into fewer fights or need bare skin to stay cool in hot environments.