We fellow human beings are amongst the primitive mammals sharing a common ancestor with chimps, monkeys and the bonobo. Although we have many features in common, the one that stands out the most is the fact that humans are not covered in fur, but why exactly is this?
As it turns out, our prehistoric ancestors were not as naked as we are today, in fact, they were covered from head to toe in fur. Studies have shown that humans lost their fur around the time early humans started walking upright. The connection between posture and fur lies with cooling. When humans started walking and running, they would sweat a lot more to cool themselves down. If they were covered in fur, they would quite literally die of heatstroke.
But what about our hair? As it turns out, humans from central Africa evolved to have darker curlier hair, which is the best at protecting the scalp from harmful sun rays and help the head to cool. Whereas humans who wandered to cooler climates developed lighter coloured and longer hair to help keep their heads warmer.
Take a look at the video below by the YouTube channel, TedEd, on Why do we have hair in such random places?