Our hair, it seems, can be a natural air-conditioner; that is, if you possess a curly mane.
Indeed, curly hair might have allowed early humans to more efficiently cool themselves and thrive under the unforgiving equatorial African sun. Our ancestors are thought to have evolved from the continent.
Research led by Penn State scientists suggests that tightly curled hair cools the scalp better than other hairstyles. And that allowed modern human progenitors to conserve water by reducing perspiration.
And it is doing so today, helping to keep our skin and brains healthy.
To test the idea, the investigators turned to thermal manikins, which are electrified so they can simulate body temperature. This also allowed them to measure the transfer of heat between the body and the environment.
The manikins were monitored wearing a variety of human-hair wigs in different styles. Testers also simulated sunshine by using lamps in a wind tunnel. The manikins were exposed to 86-degree temperatures at 60% humidity.
It was a biologic imperative for early humans to cool themselves. Having larger brains increased the organ’s heat sensitivity. And bipedalism allowed for prolonged walking and running, which increased sweat and more directly exposed the scalp to the pounding sun.
Scientists found that all types of hair reduced the amount of solar radiation reaching the scalp. But tests showed that curly hair offered the best protection and might have been common on the African continent, as it is today.
None of this, of course, helps the bald men among us. But as it turns out, we have something today that proto-humans did not: Hats.