Why Do We Have Underarm Hair?

I was in a meeting recently, and I was sitting next to a guy in a loose shirt who had his hands on top of his head. When I glanced over, I could not help but notice that I could see straight through his sleeve to his armpit. Surprisingly, I was not greeted by the usual tuft of hair, but by smoothly shaven skin. It even had a little sheen to it. First I was simply amused at the idea of a man shaving his underarms, but when you come to think about it, is not that bad a practice. This is particularly true in places, such as Nigeria, where deodorant is not widely used. Smooth skin is less sweaty and easier to clean than the hairy parts… at least that has been my experience. By the way, I actually like the smell of people here in Nigeria, everyone has their own smell.

The second thought that the shaved armpit provoked: why do we have underarm hair, it is such an unlikely place. I imagine that we were once really hairy creatures, but I guess clothing gradually reduced the need so we lost most of our hair. Hair on the head is naturally a keeper since a huge proportion of heat is lost through the head. Hair on our arms and legs can be thought of as remnants of things once necessary, but why the armpits. They are naturally warm places, yet they are places where the hair has yet to recede. So if you know why we have underarm hair, please tell me. I think I am going to google it, but perhaps someone has a good theory.

Web Guesses:

In fact these areas become hairy at puberty, that are part of our secondary sexual characteristics. When we were animals running around naked they were one of the ways of letting the opposite sex know we were old enough to be interested in breeding. Nature of course neither knows, nor cares that we now generally cover these signals with clothes, making them fairly superfluous.

Actually it was originally used to absorb and keep body odor on you because believe it or not, body odor used to be used to *attract* members of the opposite sex. I wonder why we try so hard to hide it now?

The sweat we produce all over our body is water based, except in our hairy places where it is oil based. Water based sweat is made to evaporate and keep us cool, oil based sweat is meant to stick around and make us smell funky! The hairs hold on to this perfume for longer than bare skin would. It's only the waste products of the bacteria that eat the sweat that gives you B.O.

It is believed that the functions of pubic hair include the dissemination of pheromones and protection from the friction of sexual intercourse. Natural selection may also have sustained it because it can show a potential sexual partner that the other person is sexually mature and can reproduce. Pubic hair and the growth between the tops of the legs and the buttocks, like under arm hair, helps to lubricate the areas, making movement smoother and more comfortable.