The science behind our hair

We see our hair every day. We style it, we wash it, we moan that our roots are showing or that it's falling out, we dye it, we go grey, we cover the greys, we get it cut, and consider having it all shaved off every other day. But do we really have a clue why we have it?

Truthfully, the question of where hair came from, and why, isn't the sort of thing that keeps most of us up at night. Yet here you are- you're bored, and you fancied a read, so prepare to be educated.

When you think about it, it's a bit weird that we have so much hair growing out of the top of our heads, but a relatively more normal amount growing from the rest of our bodies. Actually, way back in the caveman days, we were covered in an even coating of hair all over, a bit like monkeys. For those early humans, hair was needed for insulation, camouflage, and protection. Clothing wasn't invented back then, so hair was the only thing protecting human skin from the elements.

Over time, though, during the process of evolution, hair became less and less important on the human body. Unlike animals, humans rely massively on sweating to cool off, and having all that hair in the way means it's harder for body temperature to cool as quickly. Scientists believe that we started hunting in warmer climates- so not the UK, then- and as our intelligence increased, thus our ability to make fires, find shelter and whatnot, human hair gradually evolved to be mainly an on-the-head thing.

So, why do we still have hair on our heads? we hear you ask. For the same reason we used to have hair all over- to make heat dissipation easier. When we stand up straight, the top of our head gets the most exposure to the sun. Hair acts as a mini hat, protecting the skin from the worst of the sun's rays, and a bit of head sweat is apparently worth it for that level of protection.

It's also been theorized that we've kept the hair on our heads to stay warm in cooler temperatures. While our caveman ancestors could keep their bodies warm with animal skins and the like, our brains use 20%-25% of the body's energy, meaning it's all the more difficult to keep warm artificially (and remember, this was before the invention of hats). Not forgetting that our brains are one of the most important organs in our bodies- we'd be pretty useless without them. Hair, therefore, made an effective natural insulation for our heads during the colder nights.

Finally, scientists think hair might have stuck around so long through sexual selection. Humans have always, er, bred with other humans that they were attracted to. While women found men with facial hair attractive, men found women with long, glossy hair attractive. Sexual selection led to these features being favoured by either sex, hence why so many men can grow beards these days, and almost all women's hair can grow to long lengths.

History lesson over, all that's left to wonder is why our hair grows at a constant rate, instead of just reaching a certain point and stopping, like animal fur. The answer seems to also lie in evolution... history lesson back on.

As soon as our intelligence involved enough for us to invent knives and other cutting tools, our hair started to grow like anything. Some people argue that it might have been the other way round- long hair before knives- but that's not important. The point is, constantly-growing hair actually worked out well for us.

Having long hair helped us to protect our necks and shoulders from the sun's rays. It was also apparently useful for carrying children in, which is a bit of an amusing image. These days, it's more of a statement of self-expression than anything else. Long hair is still favoured in many women, though, proving that sexual selection is still very much a thing.

All of this leads us to wonder what's next in our hair-volution? Will we eventually lose our hair altogether? If that's the case, we're glad to be around when hair still existed. Life would be far more boring without it.