Since the beginning of recorded history, the concept of beauty and personal appearance has been a key concern for human beings. Throughout centuries people have been spending time, money and energy washing, cutting, coloring, combing, brushing and decorating their hair. The way in which the hair is presented before the others has deep sociologic roots. Hair is a message. It's the message we give to the others about our personality. Its natural function is to protect our heads against the hot or the cold weather, producing thermal insulation and conditioning. But throughout the History it became an appearance with intentional expression.
Every human hair has the structural form of a plant, with root and stem.
The stem is the visible part, just the object of our concerns. The invisible part, below the skin, is a root inserted in a bulb; this bulb is the means of nutrition for the follicle. The hair follicle is the generator of stem cells that make hair grow, and is one of the most dynamic and active organisms in our body. This follicle is fed with sebum, produced by sebaceous glands, located at its sides, which gives the hair elasticity and flexibility.
There are about 100,000 to 150,000 hairs on the human scalp, and each one is composed by 10% of water, lipids, trace elements like iron, zinc, iodine, calcium, manganese and pigments such as melanin, -which is a polymer that gives the hair its color-, and 90% proteins. These proteins are called keratins (Greek κερατίνη, meaning "horn") and are distributed in 6 or 8 layers like wrapped fibrous layers, spiraling to the left on the inner bark. The outermost of these layers is called the cuticle; it prevents drying, and influences their brightness and color.
The human hair keratin is of the type alpha keratin. It is also found in nails and animal horns. Composed by a large amount of sulfur, this type of keratin is very tough, because its fibrous layers are bound together by ties or sulfur bridges; they do not dissolve in water or saline solutions, and are elastic and resistant to breakage, heat, acidity changes and putrefaction, giving the compound a strong structural strength and long life time. The cuticle surrounds the middle part, the cortex, which holds the melanin, which produces the hair color, and a bone in the center of the hair shaft that is responsible for the hair texture and which provides the nutrients from the bulb.
The hair on the human head grows about one-half inch per month. What should be around 6 inches per year. Or what would also say, a millimeter every two days and eight or nine hours. It grows faster between the adolescence and 30 years of age, and in women more rapidly than in men. And it grows faster in summer than in winter.
The hair's shape is determined by the position in which it emerges from the scalp, and it depends on the follicle position below the scalp: upright, gives straight hair, and at an angle or curved, wavy hair. Among the barbers' tasks were always to wave the hair or to make it straight or smooth, depending on their customers' preferences.
The hair may be normal, with a balance in the emulsion of sebum, and in this case is bright and smooth, or oily, when the emulsion is rich in fatty acids. And it's bright and sticky, or dry, when the emulsion is low in fat and has little water; in this case the hair is rough and brittle.
In October 16th 1793, the queen Marie Antoinette of France was condemned to execution in the guillotine. It was said that her beautiful hair turned white, on the night before the execution. In 1535, Thomas More, manifesting his opposition to the king Henry VIII as the leader of the English Church, was sentenced to death and his hair turned gray in a single night when he was told about the execution. To Henry IV of France, in August 24th 1572, the deeds and terrors of St. Bartholomew's Night blanched his hair in one day. History is full of cases in which it is supposed to have happened, and we heard countless popular and familiar legends telling us similar facts. But...is it true? Can the hair turn white or gray in an overnight, or suddenly, as a result of a shock, or a serious depression or stress?
In 1853, Mr. Erasmus Wilson, a scientist Fellow of the Royal Society of London, looked this matter with considerable doubt. In 1911, the New York Times published an article from a journal called Deutsche Medizinische Wochenschrift, written by the German biologist L. Stieda, in which he claimed: "No matter how often these stories may be said; t he hair never changes its color; either the pigmented hairs fall out, and are replaced by white or gray hairs, or pigment production stops in a growing hair, until the colorless portion gradually replaces the other portion". Today, the science confirms this affirmation. Once your hair is grown out of its follicle, is anatomically dead, and not being for an external chemical reaction, like bleaching or decolorizing by means of acids, it's impossible to change its color. The hair has cycles of growing, and resting after which it drops out, and starts a new cycle of regeneration. When the production of melanin becomes slower, or stops, as a result of biological changes, (deficiency of Vitamin B12, thyroid imbalance, or aging) the new hair will grow colorless. This is a slow process, although it could be accelerated by hormonal changes, as a consequence of serious stress of afflictions, but it takes at least 15 days or maybe several months. Alopecia Aereata is an illness in which the hair is lost as much as 300 strands per day (the normal is 100 daily); as the colored hair is older, it will drop out first, leaving more gray or white hair in the head, and creating the false illusion that the hair "turned" white in an overnight. Legends are only legends. The reality is that the hair never turns white or gray in a single night
People with blond hair tend to have weak hair, but more of: about 150,000 in the scalp. At the other extreme, redheads have less hair: about 90,000, but thicker. And as an average, the most common people's hair is black or brown.
THE GENE MC1R AND THE RED HEADS
Biologic studies made in 1997 allowed to demonstrate a direct relation between the color of the hair and the skin and a gene: MC1R (Melanocortin 1 Receptor). The hair color is determined by a pigment, the melanin, produced by specialized cells known as melanocytes. These melanocytes produce two kinds of melanin: eumelanin (which more concentrated gives darker hair) and pheomelanin (a reddish color pigment). The combination of these two melanins gives different tonalities of hair color. Predominance of pheomelanin, gives people freckled, with red hair and fair skin. The gene MC1R works producing a protein, melanocortin, which controls the type of melanin in the hair, converting the pheomelanin in eumelanin, so the eumelanin will be more abundant. It helps to the protection of UV-radiation of the sun and makes skin and hair less exposed to external damages. But when the gene MC1R is turned off, in a dysfunctional variant, it does not accomplish its function, producing individuals with red hair, freckles and fair skin. Under these conditions, people have more tendency to develop a kind of skin cancer, melanoma. The standard gene MC1R is dominant, and the dysfunctional variant, recessive. All of us received from our parents two types of MC1R genes: we may have both of them standard, or one of them standard and another dysfunctional, or two dysfunctional variants. In the first case, conditions will be normal, giving individuals with blond, brown, or black hair and skin that tans easily. In the second case, the characteristics could be the same, but generally the skin will be freckled. And in the third case, people will have red hair, fair skin and freckles. On the other hand, red heads are more sensitive to the pain and less sensitive to anesthesia. Probably the dysfunctional variant of the MC1R gene was produced in ancient migrations to frozen areas in the Ice Age, in Europe, where less influence of the sun gave place to the mutation. This recessive form of the MC1R was found in men of Neanderthal, who lived 40,000 years ago, which makes us suppose that many of them were red heads. A mutated MC1R gene can be inherited through several generations, without ever being manifested. But, being present in the human genome, if it's one of the two genes inherited from the father, or one of the two inherited from the mother (4 in total), every child has a 25% chance of being a redhead. A redhead can show up in the family, surprisingly, without having known redhead ancestors or ginger relatives.
HAIR AND ETHNIC GROUPS
The shape of the hair varies among different human ethnic groups. However, this is a pretty outdated statement, due to the increasing mix of ethnic groups with each other in the world. Two hundred years ago the differences were much more pronounced. Today, forms of hair are more diverse than those outlined below, which are basic:
The Caucasian type (leucodermics) has, in general, less production of melanin pigmentation, not only in hair but in the whole skin, and much variation in color: blond types, red-haired and brown, dark and light, and black hair. In them, the follicle is circular and it's vertically positioned, resulting straight or slightly wavy hair. They have less segregation of sebum, which offers normal to dry hair. Hair becomes gray faster than among other groups.
The African phenotype (melanoderma) has elliptical follicles, oriented at an angle almost parallel to the skin, causing very curly hair. They also have a high production of sebum, which makes it brilliant and unctuous. Their follicles have a high production of black melanin, which gives dark hair. Pigmentation preserved longer, and grays later. Native groups in Australia (Melanesians) also have this type of hair.
The Oriental phenotype (xanthoderma) presents what is called lissothricic hairs that are straight but tend to be more straight and stiff. The follicle is circular and forms a right angle to the skin. The black melanin production is high and presents black or dark hair, and sebum production is also abundant (bright and sticky). In this group, the hair grays later than the other two groups. Among this group are also natives of Polynesia, Eskimos and Native Americans.
Just as it grows, the hair also drops out. It's common to lose between 50 and 100 hairs per day. This is because its growth has well-defined cycles. There are three levels: the first one is a growing phase, that lasts about 3 or 4 years. It is followed by a degeneration phase of three weeks, and finally it's followed by a resting phase of three months, in which it drops out. Then, the follicle begins to produce new cells and the growing cycle starts again. In general, 85% of hair in the scalp is in growing phase and 15% in resting phase. The greater or lesser duration of these periods varies from one person to another. Our body is completely covered with hair, except the palms of the hands and feet, navel and mucous membranes. We have about 5 million hairs in the body. But the hair that humans have in their bodies now, is very few compared to what it was in prehistory.