Why do men have beards?

Really, the question is why have women lost more hair in the course of our evolution than men have? If we go back to our evolutionary origins and think of the fact that we share ancestry with apes and monkeys, what is unique about humans is that we have generally lost hair. Hence, some of us hear the expression ‘the naked ape’. It’s actually not quite true to say we are hairless or the naked apes because we’ve kept hair in many parts of our body and partly because we haven’t actually lost the hair. It’s just become highly miniaturised, almost certainly because it gave an adaptive advantage in particular, helps keep cool, possibly related to having more upright posture, possibly relating to being much more active and running.

Now the question being asked is why aren’t we all equally hairless? Well to some extent, of course, people across the world vary enormously and then of course there's a big difference between men and women, and the answer most likely is to do with sex or selection. This is the second of Darwin’s great mechanisms, that selection doesn’t just work to fit people in the natural environment. It also comes about because individuals select the traits of the people they want to reproduce with, and probably, it’s the case that loss of hair, a key human characteristic, becomes more important in selecting for women because it makes them more attractive. So while all humans have been selected to lose hair, the process of how you choose a mate has extended much more in women than in men. So the real question perhaps is, why should that be attractive and I'm afraid that's probably something of a mystery.
link.

I was going to just say balls but this answer is better. Facial hair is a result of male secondary sex characteristics based on testosterone levels. Balls make testosterone. So, short answer: Balls.

Mebbe you hit puberty finally?

Seriously, things can change. I noticed that my beard is heavier (I'm 61) than it was in my 30s. FWIW, it seems to require me to shave after only 36 hours and not 48-60 hrs.

I have a beard because razor blades are damned expensive.

A better question might be, "why is body hair on humans becoming less dense and less coarse with passing generations?"

Facial hair on males probably remains simply because it was already more coarse and dense than other hair on the body. So it is the last to go. The same can probably be said for all remaining patches of body hair. And females in general probably simply had finer and thinner hair to start with, so theirs is further along the "going, going, gone" curve.

The general reduction in density and coarseness of body hair in humans is probably a secondary characteristic associated genetically with some other characteristic which is (or has been) selected for in some way. If we could figure out which gene carries the controller for body hair thickness, we might be able to deduce which other characteristic is being selected for.

The logical flaw is the assumption that just because they appear different that their purposes must also be different.

I look different from a lot of people, but that doesn't mean my purpose on Earth is all that different.

A hut looks different from a three bedroom house looks different from a mansion, but the basic purpose is the same....

Things can change, that's for sure. Crazy hormones.

I see your point, but this is just semantics. Huts don't evolve biologically. Perhaps I phrased my point too succinctly, cutting out transitional stages for time's sake, but I still maintain that nails and hair look different because they have different purposes. Just like a toe looks different from a finger. They are made of the same stuff but evolution has altered their shape and qualities based on their different purposes.

Finger nails and head hair are made of the same stuff but they look different because their purposes have become very different. One is for grip and protection, the other for thermal insulation.

I'm with DrewDad's earlier post which was much to the effect of what you are suggesting here: That women's loss of the beard was a secondary evolutionary change (a bi-product) of the primary change of lowered testosterone levels. This goes hand in hand with the different social roles that the sexes developed when we left the forest and became apex predators. Women could afford their testosterone levels dropping because they no longer required the heavy musculature which higher testosterone levels provide and which men still needed for hunting and fighting. The role of women became gathering and foraging and raising young. The evolutionary trade off was that they were physically weaker but more fertile (high testosterone levels in women can hinder fertility). This would have been advantageous at this early stage in our evolution. The loss of the beard in women was a biproduct of becoming less muscular and more fertile.

This then would kind of lead to the state of affairs where men selected the most hairless females to mate with, knowing instinctively that they would make more productive sexual partners. Thence the women with testosterone levels high enough to grow beards were bred out.

I feel this is a much better answer than "men needed to keep their chins warm" which is what some people were suggesting earlier in this thread.

http://www.livestrong.com/article/271309-high-testosterone-levels-in-women/

The article above shows what happens to women with too much testosterone. Aside from confirming the alterations testosterone brings which I outlined in my last post, it seems it also makes them more competitive and aggressive (advantageous in men for their paleolithic sexual roles, maybe less so in women).

Mr.Irish grows a mustache once a year in support of a charity that requires it. He likes it, I don't...and he's used that excuse more than once (I do tolerate it for the month of November, though).

Oh, the pic make me nauseated!

I know! Weird how in the past a hairy man may, if the ideas expounded above are right, have been extremely desirable, as it demonstrated likely strength and virility (an abundance of testosterone). Nowadays, women seem to be selecting non hairy men for breeding (if the media's idea of male beauty is anything to go by). Wonder where we'll be a million years down the line. Asians already grow far less body and facial hair. Wonder why that is.

http://www.washingtonpost.com/blogs/ezra-klein/wp/2012/08/03/why-mustaches-are-good-for-your-health/

Beards and Moustaches have been conclusively shown to be good for Men's health, as they block harmful UV rays from hitting the face - a sensitive skin area.

Cycloptichorn

No doubt shade does block harmful UV rays, but UV protection offered by beards doesn't explain why women lost theirs.

Remember, there's nothing special about the beard. It's all that's left over from when we were covered in fur. The special bits are the bald ones. Losing our body hair allowed for the more efficient cooling system of sweating to take hold. The beard just happens to be left over because testosterone, required for sexual maturity, governs it's growth.

As women's roles changed, they could afford to become more gracile (testosterone also controls some muscle growth, aggressiveness and competitiveness). The lower testosterone levels were beneficial because they made females more fertile. A side effect was losing the beard.

If it had been the other way around and the beard developed to protect sensitive faces from the sun, it's arguable that women, who also have sensitive faces, would have developed them too.

the bearded lady?

Leave my mum out of this.

It doesn't have to.

But if you want to go down that road - Cancer occurs later in life. Men are capable of producing offspring longer than women. Women would have often died in child birth prior to reaching middle age. Older men would have selected for cancer prevention. Women would have no such need for selection. None of the apes grow long beards. So the normal without selection may have been no beard.