Why do head hair grow more than other body hair

Hair on our scalp tend to grow much larger than other body hairs. Hairs on different parts of body have a certain fixed length and their length never exceed that limit. But do our head hair also have any such limit or they can grow infinitely. Even if they can reach a certain maximum limit, why do they grow comparatively longer than other body hair. We will try to find a satisfactory answer to these questions in this article.

Why do we have hair on our body ?  You may read this article before going further to increase your basic knowledge about your hair, not just hair on scalp. It tells about the basic necessity of hair. Same facts work for the scalp hair as well. Some factors made the head hair grow comparatively longer than other body hair. We will discuss those factors here.

Adaptation

Whatever we are now is due to adaptation. It is a biological process to make or modify our body according to need of our environment. In this process we loose some unnecessary features of our body and gain some new features to made our body adaptable to new environment. Hairs on our body also adapted to the changing environment. When our ancestors used to live in forests without much clothes to wear they had much more hairs on their body compared to today's human beings. Density and length of hairs on our body changed according to need and environment, but it took thousands of years for these changes to happen. Hair on head continued to grow longer than other parts of body for some reason.

Outer Appearance 

Outer appearance matters a lot in animal world. Mostly males of different species have longer head hair and beard to give them more masculine look and attract females to continue their genes. Man is also a social animal and adapted in the same way as other animals. In the modern world hair on our scalp are more an ornament for both ladies and gents. They can change you whole appearance and creates a social image of yours. However humans have evolved a lot but still we need these head hair to give us a proper look.

Protection

It protects our scalp from any external injury like cuts and scratches. Head is one of the most important organs as it contains the brain. Most of the time of the day we don't cover it and thus need more hair to give it proper protection.

• Hairs acts as cushion and can decrease the impact of a collision on head and thus saves the brain. 
• Hairs can also also protect us from ultraviolet (UV) radiation. Saving our brain from radiations might be a reason behind more dense and lengthy hair on head.
• Hairs on head help in maintaining the temperature of our scalp. Now human beings have more hairs only on that part of body which are heat release zones, such as armpits and groin. More hairs means more tendency to produce sweat and control the temperature.

Science behind longer head hair strand

Our hair have three stages of growth: Anagen, Catagen and Telogen. Anagen phase is the real growth period of a hair strand. Telogen phase is the resting and shredding phase of hair. Between these two phases comes the catagen phase which is an intermediate stage. The duration of Anagen phase decides the length of hair.  Anagen phase duration varies from few weeks to years. Most of the body hair have anagen phase of only few weeks and thus remain shorter in length. But the head hair have anagen phase of years. It makes the head hair continue to grow for years and thus making them reach the length in feets. Anagen phase of our hair depends on our genes and thus some people are more hairy than others.

If you have got some additional information about longer head hair then you may provide your insight in the comments section.