A Brief History & Biology of Human Hairs

Devoluation of hair

Introduction-

Human Hairs are strands of protein which come out from skin. It help us regulate our body temperature and afford protection. Human hairs have various colors like black, brown, blond, and grey and have distinguished patterns like straight, curly and wavy. The characteristics of hair depend on our genes, however, environmental conditions also exert some influence on hairs. It grows on scalp, torso, pubic areas and other body parts differently. Apart from its functions, human hairs have been known to portray cultural zeitgeist in the history. Since the ancient Rome of 1st century where women wore ornaments on their long braids to the elaborate hair-do of Queen Elizabeth in 1500s, hairs had a central place in cultural and social customs of humans. Let’s split some hairs and try to know about this defining feature of mammals.

Elizabeth
Queen Elizabeth I
Ann Ronan Pictures/Print Collector/Getty Images

Structure and Function of Hair

Human Hairs are composed of protein known as keratin. It spurt out from cells called keratinocytes. Keratin is also the principal component of nails, hoofs, horns, and feather. The specialty of keratin is strength. Why nail and hair look different even though both compose of keratin,  is because of  the different conformations of keratin. Hair keratin is like a thread coiled in the fashion of a spiral staircase. Numerous keratin strands intertwine together like a rope to make a single fiber of hair. Intertwining enhances the strength and toughness of hair. It grows from follicles below the skin.  Fur is nothing but hair, except that on animal. Fur provides a camouflage to many animals. The role of hair is to provide protection and warmth. Our eye brows and eye lashes modestly protect eyes from dust, dirt and sweat. However, the primary affair of hair is to help in maintaining a constant body temperature. On a winter night, you must have had goose-bumps. The erect hairs increase friction between wind and hair, which produces some heat and keeps your body warm. Also, hairs act as a barrier between surroundings and your body, and avoid exchange of body heat. It resist the exchange of body heat with the surroundings by trapping stale air around your body. It can trap more stale air than skin because of extra surface area. It also act as a cover on skin for avoiding direct contact with germs. The two essential features of hairs, that is protection and heat control, explains the peculiar presence of hairs on pubic parts.

The de-volution of Human Hairs

We did not look exactly the same as we do today. Our ancestor, the Homo erectus (ancient or early humans) had their body covered with more hairs. The early humans inherited the hairy trait from a closely related ancestor, the apes. Though, why did humans lose their excess body hair?  Appearance or disappearance of any trait is due to the advantage it affords on that species. The loss of excessive body hair must have been beneficial for the survival of our ancestors in more than one way. Our ancestors used to travel extensively for miles in open country in the pursuit of hunt and new settlements. Lack of hair suited the lifestyle as bare skin helped to speed up the cooling effect of sweat. Moreover, less hair meant less lice and bugs, which could be boastful in attracting mates. However, stripped body handicapped us in conservation of heat. Hence, we have a layer of fat below the skin to compensate the disadvantage and keep our stripped body warm. Additionally, we learned to light fire and sew clothes to tackle the adverse climate.

However, some scientists think differently about the shedding of hairs,  they believe it was an evolutionary adaptation which better suited the people who started living near seashores. The people living on seashores fed on crabs, mussels and fish, and long and thick hair was not suitable for this habitat. This is called as the “aquatic ape hypothesis”, which is supported by the fact that unlike our ancestral apes, our hair facilitates an easy flow of water when we take a dive. The reason might be anything from enhanced cooling effect, ability to make clothes, an advantage to swim, or something else, but we sure earned a great deal by shedding our body hairs. However, our entire body is almost covered with hair but too sparse to be seen. The ‘naked ape’ is not entirely naked actually.

Hominin
Hominin: an early human Courtesy: http://www.bbc.com/earth/story

Types and colors of Hair

Hair color differs within people of the same community and it also differs within people from distinct races. Some have dark hairs like black or brown and some might have lighter colors like blond or red. The substance which is responsible for imparting color to hair is called melanin, which is a pigment responsible for skin color as well. Hence, lighter hair color prevails in European and North American regions who also happen to be the people with lighter complexions. Melanin pigment is made in melanocytes, which reside close to keratinocyte (the hair spurting cells), and the melanin gives color to the hair roots. There are two kinds of melanin, the phaeomelanin, for light (blond or red) hair, and eumelanin, for dark (black or brown) hair. Our cells produce either of the two pigments depending upon our genes, which decide our hair color. In old age, the melanin production becomes less, hence no color is given to the spurted hairs, due to which they appear white or grey.

Hairs also display a dramatic range of forms like curly, wavy or straight which depends on genes. The East Asians have straighter hair whereas the Europeans can have straight or wavy hairs, and still Africans have tightly curled hairs. What gives the strand of same protein so many different forms? The answer is that keratin fibers differ in the degree of tightness when they intertwine together like a rope. The tightly bound fibers give rise to straighter hair whereas a somewhat loose binding produces waves or curls. The hair products which promise hair waving or hair straightening treatments interfere with the natural bonding of keratin and introduce some new bonding patterns. In hair waving, the adjacent bonds of keratin strands are broken with moist heat (blow dryer), and new bonds are made to form, which pull the strands to make them look curled or wavy. The procedure is reversed in the case of hair straightening.

Types of Hair
Curly, wavy and straight hair of women Courtesy: salonsuccessacademy.com/blog/what-are-different-types/

Although, hair straightening treatments are particularly popular among Indians, we must appreciate all hair types and accept the fact that all hair types are beautiful. Though, human hairs are chemically similar to fur, still mean much more to us. Hairs have a deep impact upon our psychological and social behavior. Thus, you must begin caring for them if you were ignorant, and regards to all who have been watchful. The next time when you stroke your hair, think of all the complex keratins your cells produce every day in order to keep you protected, healthy and appealing.

References

  • Nelson, David L., Albert L. Lehninger, and Michael M. Cox. Lehninger principles of biochemistry. Macmillan, 2008.
  • 1001 Science Questions Answered, Reader’s Digest (Australia) Pty, Limited, Reader’s Digest (Australia) Pty. Ltd
Guest Author
Ninad Nagarkar

Ninad Nagarkar is an academician, lecturer and research scholar in Biochemistry, and pursuing PhD in the same from Nagpur University, Maharashtra, India. He is passionately working as a science communicator at Association of Research and Training in Basic Science Education (ARTBSE), Nagpur. He is also a member of the World Pulse community which works towards achieving gender equality and social uplifting of women. His areas of interests vary from a vast range of subjects like cancer biology to arts and films.

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