It is believed that our ancestors originally had hair all over their bodies, just like monkeys do today. However, we still do not know exactly why the hairs on the rest of the body became short and thin, and why, on the other hand, only the hairs on the head remained thick and long.
We can only guess. Let us consider the role of hairs as we know them today. There are three roles that are commonly understood for hair. The first is to protect the body from heat, cold, and wounds, the second is to show the difference between men and women, and the third is to cover the body. When we think about the existence of hairs on the head, the first one, protecting the body, is probably the most applicable. This is because the human head is the most important part of the body.