Just as feathers are characteristic of birds, so hair is characteristic of mammals. Why do mammals have hair? There is a variety of reasons. Let’s consider some of them.

The chief value of hair is that it conserves the heat of the body. In the tropics, it may serve an opposite function. Certain tropical animals are protected from direct sunlight by their hair.

Very long hair on certain parts of the body usually serves some special purpose. For instance, a mane may protect an animal’s neck from the teeth of its enemies. Tails may act as flyswatters. Crests may attract the opposite sex. In the case of the porcupine, its stiff quills-formed of bunched-up hair help it to attack its enemies. Hair may also serve as organs of touch. The whiskers of cats have special nerves that respond quickly to touch.

So you see that hair can serve a different purpose with different mammals. How about human beings? We know that beautiful hair in a woman can be very attractive to men. But we must assume that hair on human beings formerly played a more practical role than it does now.

When an infant is born, he is covered with a fine down. This is soon replaced by the delicate hair which we notice in all children. Then comes the age of puberty, and this coat of hair is transformed into the final coat of hair which the person will have as an adult.

The development of this adult hair coat is regulated by the sex glands. The male sex hormone works in such a way that the beard and the body hair are developed, while the growth of the hair on the head is inhibited, or slowed down in development.

The action of the female sex hormone is exactly the opposite! The growth of the hair on the head is developed, while the growth of the beard and body hair is inhibited. So women don’t have beards because various glands and hormones in their bodies deliberately act to prevent this growth.

To explain why this is so, and why men’s glands and hormones act to promote growth of beards, we probably have to go back to the early history of man. At one time, the function of the beard was probably to make it easy to tell men and women apart at a distance. It also probably served to give the male an appearance of power and dignity, and so make him more attractive to the female. Nature was helping man to attract the opposite sex, just as she does with other creatures.