Why do humans have curly hair?

A new study says that it is to help us keep cool!
A new study reveals that curly hair could be the peak of an ancient adaptation to keeping cool. (ID 95846266 © Pojoslaw | Dreamstime.com)

Though humans are mammals, we have a number of traits that are quite distinctly ours.

Walking upright is one. So is have opposable digits for gripping and manipulating objects (while we're not completely alone in this trait, we are far more advanced at it that others).

Then there is our hair. Compared to other mammals, are bodies are essentially naked—no fur or even tough skin, and only a smattering of hair here and there. Except upon our heads.

Those are mysteriously covered in hair. And wide variety of hair, too. Known as scalp hair, it comes in different colours, different thicknesses, and different textures. Some of us even have hair that grows in tight curls. No other wild mammal has this kind of hair. So why do we?

A new study published on the site bioRxiv decided to look into why humans are, well, naked except for our scalp hair. And in the process, they believe that they also discovered that curly hair provided a distinct advantage in hot settings.

Why is it (t)hair?

Human hair can be thick and abundant on our head ... but barely there everywhere else. This is very different from other mammals. (Wikimedia Commons)

Humans are pretty fond of cutting their hair a certain way to look cool. ("Did you just get a cut? Sweet 'do, my friend!")

But according to this research, our scalp hair actually helps to keep us physically cool.

The scientists tested out a variety of different human hair wigs in a series of different wind, humidity, and solar heat conditions. They also tested a bald, or naked, scalp. The goal was to try and see if hair provided any evolutionary advantages in terms of helping us manage our body temperature. Or in other words, keep cool.

And whether or not certain types of hair did it better than others.

This would help to prove that there was an evolutionary reason for us to have the type of hair that we do. After all, most other animals have some traits that allow them to manage their body temperature by either staying warm or keeping cool. Why not us?

Staying cool

After going through the results, the researchers concluded that our scalp hair does help keep us cool. As did the rest of our mostly naked body. Here's how it works.

The scalp hair shields us from solar radiation. It is a protective barrier between our head and the Sun bombarding rays on our poor noggin. Meanwhile, the rest of our hairless body allowed heat to easily radiate away from us. The result? Much cooler humans, especially in the African grasslands where modern humans originated from!

And remember what we said about curly hair? According to the study, tight curly hair was the most effective at keeping us cool.

So the next time you're thinking about a super-short-and-close haircut to welcome the summer, maybe think again. Turns out, that hair of yours is pretty cool as it is!

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