The human body is covered in follicles that produce hair. Basically, the hair is a protein filament called keratin growing in the deep dermis. Hair is a defining trait of mammals. As a simple structure, the hair protects the human body from damage. It develops on the epidermis and grows away from it to form a protective layer. The human hair has a number of uses:
According to anthropologists, humans had a protective coating of hair all over their body to regulate body temperatures. As primates on all fours, the entire body was exposed to UV rays and hence the covering. With our gradual evolution to the standing, position hair was not required everywhere and that’s when we began losing it. Even modern humans maintain the same number of hair follicles as apes.
There are three phases to hair growth:
The average growth rate of the hair is about 0.3 to 0.4 mm per day though growth rate differs from individual to individual. Melanin produced in the hair follicle is the pigment responsible for the colour of the hair. Hair turns grey as we grow older because the pigment cells die.
One of the most interesting facts about hair is that the human foetus develops all of its follicles (about 5 million of them) by week 22 in the womb. We do not generate any new follicles during the rest of our lifetime!