Why, evolutionarily speaking, do men have beards and women don’t?

…We both have armpit, leg and arm hair in similar amounts, so why do men benefit from a beard and women don’t?!

Movember! by fengschwing, on FlickrGood question – let’s try and get to the root of it. (Please, no – Ed.)

Why do men typically have more facial hair?  Well, as with many characteristic male traits, the answer lies with testosterone (you know, that hormone that makes you want to burp, fight, and tell your in-laws offensive jokes?). As well as having many other important effects, testosterone increases the growth rate of facial hair, making it possible for men to form some rather handsome beards.  In fact, one of the side effects of testosterone therapy can be a hairier face.

But why would this be a good thing evolutionarily? It’s hard to say – human evolution happened over hundreds of thousands of years, and, for the majority of that time we were probably just hitting each other with clubs. (Possibly – Ed.) However, there are a couple of plausible explanations…

The first such explanation is that hair keeps us warm. You can imagine the hunter-gatherer lifestyle of the early man involved braving some pretty chilly weather. In this respect, increased facial hair may have helped ward off frostbite, leaving our ancestral hero’s lips intact for a good smooch with the missus when he got home to his cave.

Another explanation could be sexual selection – the idea that evolution favours traits which make you more attractive to the opposite sex. Perhaps early human females found beards an irresistible aphrodisiac. We know that facial hair is somewhat correlated with testosterone, and testosterone levels are correlated with male fertility… so it makes sense then, to go for males with bushy beards who are just brimming with ‘man-ness’.

Alternatively, there’s always the possibility that originally females also had large amounts of facial hair, and it was a chap’s preference for less facial hair in a potential mate that caused women to lose hair this over time.

I hope that gives you something to think about, Sarah. For now, I beard you farewell. (I’m so sorry – I couldn’t resist.)

Question from Sarah Cottle

Answer by Ross Harper

Article by Ross Harper

November 22, 2013

A biologist straight out of Cambridge University, Ross spent two years heading his own technology start-ups: BuyMyFace.com and Wriggle Ltd. As he begins his neuroscience PhD at UCL, Ross is living proof that you can take the boy out of the lab, but not the other way around. Between devising his latest crazy schemes, Ross makes an effort to eat (pizza), sleep (two pillows), and exercise (skiing/rugby/swimming). Follow him on Twitter @refharper.

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