It’s an interesting-enough question to ask ‘why do people have hair on their heads, but not on the rest of their bodies?’
Some have speculated that it has to do with our propensity for fishing and swimming. Given how most mammals have fur, while marine mammals do not, having hair on our heads appears to be a kind of evolutionary compromise. But it seems like an odd one. Why the head? Why not–say–the arms? And why have hair at all, if it interferes with swift swimming? Why not be hominid naked mole rats or killer whales, since we are evidently capable of keeping warm in other ways, and have been doing so for tens of thousands of years?
A possible answer to this question occurred to me when talking about dog breeds with a family member.
This mop-like creature is a canine, known as the komondor:
Among flock-guardians (not to be confused with sheep-dogs: protectors and herders have different roles), the komondor is among the best. And its… “unique” hairstyle is a component of its success in this role.
Aside from allowing it to blend in with the sheep, the natural dreadlocks on the komondor serve as a kind of natural armor against the teeth of wolves. They were such effective wolf-killers, in fact, that some credit them with completely depopulating Hungary of its native packs.
If dreadlocks serve as a kind of protection against sharp teeth, might they serve as protection against other sharp things as well?
Left to its own devices, human hair will naturally grow long and will dreadlock, forming a ring around the most vulnerable target for slicing swords or axes: the neck.
I can’t pretend to have a complete and coherent explanation for why men have the beards which complete this natural ring of neck-armor, while women lack them. But intuitively, it is obvious that men have greater need for complete neck-protection. Perhaps it has to do with the fact that women’s evolutionary success tends to depend more highly upon indications of fertility, which are often displayed in the face, so the extra neck protection would cost more in evolutionary potential than they would gain. Men, meanwhile, may have been historically more likely to get decapitated than they are to completely strike out in the dating pool.
This hypothesis would get to the real answer behind the question ‘why do men have beards?’ which most “answers” kind of dodge. It seems that the prevailing opinion is that beards signal aggression and dominance, and indicate higher testosterone levels which may increase attraction. But why would women be attracted to beards in the first place, and why would higher testosterone correlate with beards? What would be the actual advantage there?
There are, of course, a number of possible answers: perhaps, like the peacock tail, the beard is a demonstrative handicap indicating health. Perhaps it serves some other mechanical function (like filtering?) of which we are not aware. But if the dreadlocked beard and hair formed a protective neck-ring, which gave at least partial protection, it would provide an explanation for why beards might correlate with testosterone in the first place, why we tend to associate them with physical dominance, and why they might be attractive to a partner, despite making it slightly more difficult to kiss, which is an arguably more important tool in gauging hormonal health and genetic compatibility than body hair.