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hair

  (hâr) pronunciation
n.
    1. Any of the cylindrical, keratinized, often pigmented filaments characteristically growing from the epidermis of a mammal.
    2. A growth of such filaments, as that forming the coat of an animal or covering the scalp of a human.
  1. A filamentous projection or bristle similar to a hair, such as a seta of an arthropod or an epidermal process of a plant.
  2. Fabric made from the hair of certain animals: a coat of alpaca hair.
    1. A minute distance or narrow margin: won by a hair.
    2. A precise or exact degree: calibrated to a hair.

[Middle English her, from Old English hǣr.]


 
 

Nonliving, specialized epidermal derivatives characteristic only of modern mammals. However, it is now thought that hair was present in at least some therapsid reptiles. It consists of keratinized cells, tightly cemented together, which arise from the matrix at the base of a follicle. A follicle is a tubular epidermal downgrowth that penetrates into the dermis and widens into a bulb (the hair root) at its deep end. The follicle, together with a lateral outgrowth called the sebaceous gland, forms the pilosebaceous system. Rapid cell production in the matrix, and differentiation in the regions immediately above, produces a hair shaft which protrudesfrom the follicle mouth at the skin surface. See also Gland.

Hairs are not permanent structures but are continually replaced throughout the life of a mammal. In some species, for example, the rat, hamster, mouse, chinchilla, and rabbit, the replacement pattern is undulant, and waves of follicular activity can be traced across the body. In other species, for example, humans, cats, and guinea pigs, each follicle appears to cycle independently of others in the immediate area.


 

Hair is present in differing degrees on all mammals, and its most important function in those other than human is to conserve body heat by insulating against cold. Humans are the most hairless of all mammals, and yet hair occupies a central place in human development and sense of self. Whether it is the gradual decrease of hair leading to male baldness, the loss of pigment leading to white or grey hairs and signalling the onset of middle age, or the adolescent desire for the pubic hair that signals approaching adulthood, hair often tells others something about our place in culture.

Hair types and styles have, at various times, in various countries and on various continents, come to be associated with definitions of race, the possibility of being or becoming the right kind of woman, with radicalism or revolution, and with the right to occupy a particular social space in a class hierarchy. While often discussed as a personal statement of style or fashion, humanity's relationship to hair is far more complicated.

During the monarchy in France, the prince's hair, for example, was never cut — it was curled and pampered. Rastafarian followers of the early twentieth-century Ethiopian religious leader Haile Selassie not only refused to cut theirs, but were forbidden to comb it either. Early records indicate that the ancient Egyptians, men and women alike, shaved their hair off and wore wigs. Prostitutes in Nazi Germany were forced to shave off their hair so they could be easily identified and shamed. In the post-war period, women who had collaborated with the Nazis were similarly forced to shave their heads. Delila cut off Samson's long hair so that she could strip him of his fabled strength and power. As a sign of respect for the law and British custom, judges and lawyers during America's colonial period wore powdered wigs over their natural hair. Rapunzel let her hair cascade out of a window and down a tower so that Prince Charming might climb up and rescue her from imprisonment. Among the Yoruba people, hair signifies aesthetic value; and for East African pastoral peoples, such as the Pokot and Samburu, its styling indicates age status. A 1970s American Broadway musical, Hair, received numerous awards and set records for attendance.

Individual human hairs vary in colour, diameter, and contour. The different colours result from variations in the amount, distribution, and type of melanin pigment in them, as well as from variations in surface structure that cause light to be reflected in different ways. Hairs may be coarse, or so thin and colourless as to be nearly invisible. Straight hairs are round in cross section, while wavy hairs are alternately oval and round; very curly and kinky hairs are shaped like twisted ribbons. During the nineteenth century, renowned social scientists posited relationships between some of these variations in hair type and intelligence, or the potential for civilized behaviour, and indeed, in some instances, saw them as a marker of humanness.

In his 1848 Natural History of the Human Species, Charles Hamilton Smith, for example, suggested that hair type is crucial for defining the three typical ‘stocks’, or races, of mankind: the bearded Caucasian, the beardless Mongolian, and the woolly-haired Negro. His work included a chart which positions the ‘woolly-haired’ at the base of a triangular hierarchy and the Caucasians at the apex. Smith's ‘woolly-haired race’ became a metaphor for African physical traits which served prima facie as evidence of racial difference, such as mental ‘lack’, and as a justification for slavery and racial discrimination. The lingering effects of such pseudo-scientific theories may help to explain why people of African descent continue to spend billions of dollars each year trying chemically to alter the texture of their hair in order to make it straight, as opposed to ‘woolly’.

Each hair grows from a hair follicle in the deep layer of the skin. There are different types of hair at different stages in life, and in different parts of the body. The first to develop is the lanugo, a layer of downy, slender hairs that begin growing in the third or fourth month of fetal life and are entirely shed either before or shortly after birth. During the first few months of infancy appears fine, short, unpigmented hairs called down hair, or vellus. Vellus covers every part of the body except the palms of the hands, the soles of the feet, undersurfaces of the fingers and toes, and a few other places. At and following puberty, this hair is supplemented by longer, coarser, more heavily pigmented hair, called terminal hair, that develops in the armpits, genital regions, and, in males, on the face and sometimes on parts of the trunk and limbs. The growth and the distribution of hair are under the influence of the sex hormones. The hair of the scalp, eyebrows, and eyelashes are of separate type and develop fairly early in life. On the scalp, where hair is usually densest and longest, the average total number of hairs is between 100 000 and 150 000. Human hair grows at a rate of 10-13 mm/month. While hair texture and type was of importance for nineteenth-century social scientists in the shaping of racial hierarchies, for middle-class women in Christian countries, hair length has been important in the shaping of hierarchies of femininity. In part due to a passage in the King James version of the Bible (‘if a woman have long hair, it is Glory to Her’ 1 Cor: 11-15), such women the world over have often been urged by society at large, and by patriarchs in their individual households, to wear their hair in long, precisely styled hair-dos that they refrained from cutting. During the Victorian period the long, elaborately-styled hairdos favoured by the middle classes signalled wealth, leisure time, and modesty (it was almost impossible for a woman to fix her hair in one of the fashionable styles without the paid help of a hairdresser, and the styling could often take three hours or more). During the 1920s, women who ‘bobbed’ or cut their hair to ear length caused a furore in Europe and the US. The new hair style, which went hand in hand with shockingly at, or above, the knee skirt lengths was seen as immodest and outside of prevailing standards of decency. This was true in part because bobbed hair was immediately favoured by women in the ‘world's oldest profession’ due to its ease of care.

By the late 1960s, long hair came to be back in vogue amongst male and female youth in America. However, far from being a return to the earlier ideals of propriety often associated with long hair, lengthy hair now denoted a counter culture or radical stance in both white and black communities. One of the surest ways for white teenagers and young adults to identify themselves as in rebellion against prevailing middle-class ideals and culture, and governmental political strategies, was to wear their hair in the long, straight styles favoured by hippies, flower children, and political activists. During this same period afros came to be a popular style in African-American communities. The afro was understood to denote black pride, which became synonymous with black nationalism, activism, and a radical political consciousness. This sentiment moved sharply against the prevailing integrationist ideology and evidenced a belief that the gains of the Civil Rights Movement were not broad-based enough, and was a style favoured by radical groups like the Black Panthers.

In addition to the presence or absence of hair, hair texture and styling have played a long and important role in human history. It is not clear just why hair has come to mean so very much to so many people, but there is no mistaking the important role that hair has played in the process of identifying a relationship to a particular culture or subculture. Hair can lead to acceptance or rejection by certain groups and social classes, and its styling can enhance or detract from career advancement. What many envision as a personal statement is also implicated in an intricate web of religious and social politics.

— Noliwe Rooks

See also baldness; sex hormones; skin.

 

Hair condition may be affected by a person's diet and health. Bouncy, shiny hair is usually a sign of a well-nourished person in good overall health. Dry, dull, and lusterless hair often belongs to malnourished people in poor health.

Beauticians claim that more than fifty nutrients are needed for healthy hair. A deficiency of proteins (e.g. in anorexics) can lead to hair loss. Lack of vitamin A or linoleic acid (an essential fatty acid found in sunflower oils) may reduce oil secretion from sebaceous glands attached to hair follicles, leaving hair dry and lifeless. Lack of vitamin C causes hair to split and become dry. Copper deficiency sometimes causes hair to lose colour. However, hair condition is affected by so many other environmental factors (e.g. wet weather, smoke, hair sprays, and shampoos) that it is not a reliable indicator of nutritional status.

 

[back-formation from hairy] The complications that make something hairy. “Decoding TECO commands requires a certain amount of hair.” Often seen in the phrase infinite hair, which connotes extreme complexity. Also in hairiferous (tending to promote hair growth): “GNUMACS elisp encourages lusers to write complex editing modes.” “Yeah, it's pretty hairiferous all right.” (or just: “Hair squared!”)


 

Mention of hair in its military context conjures up visions of the radical haircuts applied to generations of conscripts, to help treat head wounds, promote hygiene, aid identification of deserters, mark a man's transition from civilian to soldier, and underline the equality of recruits. ‘I never saw so much hair in all my life, ’ wrote Vietnam veteran David Parks in GI Diary. ‘It was all mixed up on the floor together, white hair, Spanish hair and soul hair, all going the same route.’ The 1960s reaction against short hair was in many ways a political as well as a counter-cultural phenomenon.

The military symbolism of hair is more complex. Usually, in common with uniform, it followed the dictates of fashion. Tenth-century warriors often wore their hair long in the Scandinavian style. The Normans shaved back and sides in a distinctive manner shown on the Bayeux Tapestry, but in the late 11th century longer hair, often worn with a beard, became fashionable once more. Knights going on a long campaign usually cut their hair short to help helmets fit snugly. A ‘pudding-basin’ cut, often seen on memorial brasses, shows hair thick but clear of the ears, probably to assist in cushioning the helmet.

The long but simply dressed hair of the early 17th century was succeeded by more elaborate fashions. Wigs, initially full-bottomed but neater as the 18th century wore on, were worn by officers, and soldiers had their hair pomaded, powdered, and drawn together at the back in a ‘club’ or queue. The queue generally disappeared in the early 19th century, though Napoleon's Old Guard retained it, a grenadier describing his ‘six inch queue tied by a worsted ribbon with 2-inch ends and pinned with a silver grenade’. It is commemorated in the British army by the Royal Welch (sic) Fusiliers, whose officers wear a ribbon on their collars to represent the ribbon binding the queue. As the queue declined, so side-whiskers (later called sideburns after the magnificent facial adornment of US Gen Burnside) became popular. There were wide variations, from the braided lovelocks of French soldiers of the Revolutionary era to the bushy whiskers of Victorian officers.

Often, too, hair was part of an attempt to ape the successful or the warlike. Eighteenth- and early 19th-century hussars tried to look like wild men from the great plain of Hungary, long plaits often weighted with pistol balls and long, waxed moustaches which were elaborately tied up at night. When young Marbot joined the French 1st Hussars in 1798 his mentor, Sgt Pertelay, had ‘moustaches half a foot long waxed and turned up to his ears, on his temples two long locks of hair plaited, which came from under his shako and fell on his breast’. Marbot bought sham pigtails from the regimental barber, but as he was too young to grow a moustache, the helpful Pertelay used blacking to paint two huge hooks on his face.

The Turkish fashion of wearing a long tuft of hair atop an otherwise shaven head spread not only across many armies of the Muslim world, but also into Russian Cossack irregular light cavalry. During the Seven Years War they were sent to instil fear in the German population of East Prussia. ‘They are an olive colour, ’ recorded an observer, ‘and their faces full of wrinkles, with very little or no beard. They shave their heads, leaving only a tuft of hair on the crown.’ The practice of wearing a scalp lock extended as far west as French hussars of the early 18th century.

Grenadiers also cultivated facial hair. In Napoleon's Guard moustaches were a seasonal occurrence, shaved off on 1 December and not allowed back until 1 March: from 1806-7 they were worn all the time. Infantry units often included pioneers (sapeurs in France) responsible for light construction or demolition work, and they wore leather aprons (ostensibly to protect their uniforms), carried axes, and often had full beards. Pioneer sergeants remain the only men in the British army normally allowed to sport beards. French sapeurs marched with the drummers as part of their regiment's tête de colonne, and very impressive they looked. A British soldier in the Peninsula wrote: ‘Their hats, set round with feathers, their beards long and black, gave them a fierce look. Their stature was superior to ours: most of us were young. We looked like boys; they like savages.’

Although the moustache was not compulsory in the British army of the Edwardian era, shaving the upper lip was forbidden. An officer was successfully court-martialled for shaving in 1916. When the sentence passed through the hands of Lt Gen Macready, adjutant-general of the British Expeditionary Force (BEF), on its way to the C-in-C for confirmation, Macready recognized the absurdity of the regulation and had it revoked. Facial hair retains symbolism even at the end of the 20th century: the gay community's affection for the moustache has dramatically reduced its popularity in the US army (see homosexuality and the armed forces).

— Richard Holmes

 

Threadlike outgrowths of the skin. Babies shed a layer of downy, slender hairs (lanugo) before or just after birth. The fine, short, unpigmented hairs (vellus) then grow. Starting at puberty, terminal hair, longer, coarser, and more pigmented, develops in the armpits, crotch, sometimes on parts of the trunk and limbs, and, in males, on the face. Scalp hair, eyebrows, and eyelashes are different types. The number of scalp hairs, which grow about 0.5 in. (13 mm) per month, averages 100,000 – 150,000. The hair shaft (above the skin) is dead tissue, composed of keratin. Only a few growing cells at the base of the root are alive. Hair is formed by cell division at the base of the follicle (a tiny pocket in the skin), part of a cycle of growing, resting, and falling out. Vellus lasts about four months, scalp hairs three to five years.

For more information on hair, visit Britannica.com.

 

This makes many appearances in superstitions, cures, tales, popular errors, and divination. One should be particularly careful in the disposal of hair after cutting or brushing, as such removable parts of the body can be used in witchcraft against you. Birds must also be prevented from using your hair to make their nests, as this would mean a headache, or if a magpie, death within a year, so the only safe method of disposal is to burn it (Opie and Tatem, 1989: 184). Most regional folklore collections include examples of the divinatory use of hair. When it is thrown on the fire, for example, if it burns brightly then a long life is to be expected, but smouldering means the opposite. A single hair drawn between the nails of finger and thumb indicates the character of its owner.

A belief reported from the 17th century to the present day is that if a person's hair grows into a low point over the forehead, like a peak, she/he will be widowed soon—hence the name ‘Widow's peak’. Schoolchildren had a particularly useful belief: if you place a single hair across the palm of your hand, it will split the cane with which you are being chastised, or at least it will considerably lessen the pain felt (Harland and Wilkinson, 1873: 225; N&Q 11s:11 (1915), 277-8). See also onion for a similar idea. Also, ‘In my childhood I used to be told that if you swallowed a long hair it would twine about your heart and kill you’ (N&Q 8s:10 (1896), 47), an image which is surprisingly old, being found in Thomas Middleton's play, The Witch (IV. i): ‘… let one of her long hairs wind about my heart, and be the end of me.’

Porter (1969: 81-2) gives several recipes for traditional hair care from Cambridgeshire, including tobacco and pepper to cure ringworms, and the use of goose grease or bear's grease to keep hair healthy. A Lincolnshire woman, however, swore by hedgehog fat for this purpose (Sutton, 1992: 147) and many writers comment that rosemary leaves make an excellent hair tonic or rinse. Since at least the 16th century it was thought essential to comb your hair the right way (Lean, 1903: ii. 24), and if you want your hair to grow back thick and luxuriant, it must be cut when the moon is waxing. It was considered unlucky to cut hair on Friday, and Good Friday was the worst day of all to do it; a baby's hair should never be cut until it is twelve months old (N&Q 2s:12 (1861), 500).

There has been a long-standing prejudice against red hair in Britain since at least c.1200. At best, red-haired people were considered unreliable and hot-tempered, and archetypal evil people such as Judas Iscariot and Cain were usually depicted with red hair and beard. Another explanation sometimes given is that the Danish invaders had red hair, and red-haired children were sometimes quoted as evidence of their mother's infidelity (Harland and Wilkinson, 1873: 225; N&Q 12s:2 (1916), 128, 196-7, 239, 379; 12s:5 (1918), 194, 218; Opie and Tatem, 1989: 325-6).

A regularly reported cure for whooping cough is to take a hair from the afflicted child, place it between two slices of bread, and give them to a dog to eat. The dog will get the cough and the child will be cured (Porter, 1969: 90, and many others). Two widespread ‘popular errors’ concerning hair are the beliefs that hair could continue to grow after death, and that a person's hair could turn white overnight through extreme fear or mental anguish. The latter idea still turns up as a motif in some contemporary legends. See the correspondence in N&Q 4s:6 (1870); 4s: 7 (1871); 6s:6 (1882); 6s:7 (1883); 6s:8 (1883); 6s:9 (1884); 7s:2 (1886); 7s:3 (1887); 7s:4 (1887); 7s:7 (1889); 10s:9 (1908); 10s:10 (1908).

Bibliography
The full bibliography list is available here.

  • Opie and Tatem, 1989: 184-6, 325-6, 445-6
 
slender threadlike outgrowth from the skin of mammals. In some animals hair grows in dense profusion and is called fur or wool. Although all mammals show some indication of hair formation, dense hair is more common among species located in colder climates and has the obvious function of insulation against the cold. Other functions include camouflage and protection against dust and sand. The long, sensitive hairs, called tactile hairs, that are located around the mouth area of most mammals are extremely sensitive to touch. Each hair filament originates in a deep pouchlike depression of the epidermis, called a hair follicle, which penetrates into the dermis. The root of the hair extends down into the hair follicle and widens into an indented bulb at its base. Extending into the indentation is the papilla, the center of hair growth, which contains the capillaries and nerves that supply the hair. Newly dividing cells at the base of the hair multiply, forcing the cells above them upward. As the cells move upward, they gradually die and harden into the hair shaft. The hair shaft has two layers, the cuticle and the cortex. The cuticle (outer layer) consists of flat, colorless overlapping cells; below the cuticle is the cortex, containing pigment and a tough protein called keratin; it forms the bulk of the hair shaft. Coarse hair, such as that of the scalp, contains an additional inner core called the medulla. Hair is lubricated by sebaceous glands that are located in the hair follicle. Illness or stress may lessen the secretion of pigment, which normally gives color to hair, and cause the hair shaft to whiten. However, the normal process of whitening that comes with age is determined by heredity. In humans, scalp hairs are generally shed every two to four years, while body hairs are shed more frequently. Straight-textured hair, round in cross section, is common among Native Americans, Eskimos, and Mongolic peoples. Kinky or woolly hair, flat in cross section, prevails among the dark peoples of Africa, Australia, and elsewhere. Wavy or curly hair, common among Caucasians, is oval in cross section. The color of hair is determined by the amount of pigment and air spaces in the cortex and medulla. Hair color and texture are inherited characteristics.


 

Hair has had an occult significance since ancient times. It seems to have a life of its own, since it may continue to grow after the death of the body. It has been regarded as a source of strength and sexuality and has played a part in religion and magical rituals. The Hebrews developed a number of customs relative to hair that served to separate them from their pagan neighbors, a fact which is played out in the story of Samson and Delilah (Judg. 16:4-22)

In various cultures, individuals dedicated to service of the priesthood have undergone ritual cutting of hair, and the tonsure of priests is said to have originated in Egypt (see the writings of Herodotus). In Hinduism, there are hair rituals for youths, and those who become celibates have their heads formally shaven. The association of hair with sexuality has given hair as a symbol remarkable force, and distinctions between male and female hair have emphasized sexual attraction.

Since the hair is believed to be intimately related to the life of an individual, it has magical significance in witchcraft rituals, and people in many civilizations have been at pains to prevent their hair from falling into the hands of an enemy, who might use it for black magic.

There is even a school of character reading from the hair, known as trichsomancy.

Extreme fright or ecstatic states have caused hair to literally "stand on end" in the goose-flesh condition of horripilation.

Sources:

Berg, Charles. The Unconscious Significance of Hair. London: Allen & Unwin, 1951.

Cooper, Wendy. Hair: Sex Society Symbolism. London: Aldus Book, 1971.

 

1. a threadlike keratinized epidermal structure developing from a follicle sunk in the dermis, produced only by mammals and characteristic of that group of animals. Also, the aggregate of such hairs.
2. various other threadlike structures.

  • auditory h's — hairlike attachments of the epithelial cells of the inner ear.
  • awn h. — in cats, a short thick, bristly hair underneath the top coat.
  • h. beds — coat hairs occur in groups of about three primary follicles and a variable number of secondary follicles.
  • burrowing h. — one that grows horizontally in the skin.
  • h. cells — sensory neuroepithelial cells which have hair-like processes; found in organ of Corti, ampullary crests and utricle and saccule of the inner ear.
  • club h. — a hair whose root is surrounded by a bulbous enlargement composed of keratinized cells, preliminary to normal loss of the hair from the follicle.
  • h. coat — see coat (1).
  • cover h. — see guard hair (below).
  • h. follicle — one of the tubular invaginations of the epidermis enclosing the hair roots and from which the hairs grow.
    Longitudinal section of hair follicle. By permission from Smith BP, Large Animal Internal Medicine, Mosby, 2001
  • h. follicle unit — see apopilosebaceous complex.
  • h. granuloma — granuloma in the esophageal wall caused by swallowed hairs acting as foreign bodies.
  • h. growth cycle — a period of growth, called anagen, is followed by a transitional stage, called catagen, and then a period of inactivity in the hair follicle, called telogen, lasting until the cycle starts again. The duration of each stage varies with the species, anatomical location, genetic influence, and a variety of environmental and physiological factors.
  • guard h. — the coarse, stiff and often longer and more prominent hairs in a haircoat with an undercoat. For example, the darkly colored, outer hairs of a German shepherd dog. Called also primary hair, master hair, cover hair.
  • ingrown h. — one that has curved and re-entered the skin.
  • lanugo h. — the fine hair on the body of the fetus.
  • master h. — see guard hair (above).
  • primary h. — see guard hair (above).
  • ringed h. — see thrix annulata.
  • secondary h. — finer and growing from a more superficial follicle than a guard hair; forms the undercoat.
  • sensory h's — hairlike projections on the surface of sensory epithelial cells.
  • sinus h. — the vibrissae or whiskers located on the muzzle and face of many species has an endothelium-lined blood sinus between the inner and outer layers of the dermal portion of the follicle with a rich nerve supply. This structure serves to increase sensory perception.
  • specialized h. — includes auditory, guard, sensory, tactile, taste, tylotrich hairs (see this list).
  • h. streams — the hairs in the coat of animals are inclined in one or other direction so that collectively they create streams that meet at vortices or cowlicks.
  • tactile h's — hairs particularly sensitive to touch.
  • taste h's — short hairlike processes projecting freely into the lumen of the pit of a taste bud from the peripheral ends of the taste cells.
  • tipped h. — one with a different, usually darker, color at the tip; seen in Chinchilla cats.
  • tylotrich h. — special hairs that act as rapid-adapting mechanoreceptors; large, primary follicles with a ring of neurovascular tissue around them. Always associated with a tylotrich pad, a local area of epidermal thickening with a layer of highly vascular and well-innervated connective tissue below.


 
pronunciation

IN BRIEF: Any of the thin growths, like threads, that come from the skin of animals and human beings.

pronunciation I think it's beautiful the way the sun lights up the hair in your ears. — Frank Burns

Tutor's tip: A "hare" (a large rabbit) can have very soft and valuable "hair" (the furry outgrowth of the body).

 

Quotes:

"It's not the hair on your head that matters. It's the kind of hair you have inside." - Garry Shandling

"Gray hair is a sign of age, not of wisdom." - Greek Proverb

"Gray hairs are death's blossoms." - English Proverb

"The hair is the richest ornament of women." - Martin Luther

"Babies haven't any hair; Old men's heads are just as bare; between the cradle and the grave lie a haircut and a shave" - Samuel Hoffenstein

"By common consent gray hairs are a crown of glory; the only object of respect that can never excite envy." - George Bancroft

See more famous quotes about Hair

 
Wikipedia: hair


Human hair under 200-times magnification
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Human hair under 200-times magnification
A strand of human hair under magnification
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A strand of human hair under magnification

Hair is a filamentous outgrowth of protein, found only on mammals. It projects from the epidermis, though it grows from hair follicles deep in the dermis. Although many other organisms, especially insects, show filamentous outgrowths, these are not considered "hair". So-called "hairs" (trichomes) are also found on plants. The projections on arthropods, such as insects and spiders are actually insect bristles. The hair of non-human mammal species is commonly referred to as fur. There are varieties of cats, dogs, and mice bred to have little or no visible fur. In some species, hair is absent at certain stages of life.

The primary component of hair fiber is keratin. Keratins are proteins, long chains (polymers) of amino acids.

Human hair

Body hair

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Historically, several ideas have been advanced to describe the reduction of human body hair. All were faced with the same problem that there is no fossil record of human hair to back up the conjectures nor to determine exactly when the feature evolved. However, recent research on the evolution of lice suggests that human ancestors lost their body hair approximately 3.3 million years ago.[1]

Savanna theory suggests that nature selected humans for shorter and thinner body hair as part of a set of adaptations to the warm plains of the savanna, including bipedal locomotion and an upright posture. There are several problems (including balding) with this theory, not least of which is that cursorial hunting is used by other animals that do not show any thinning of hair.

Another theory for the thin body hair on humans proposes that Fisherian runaway sexual selection played a role here (as well as in the selection of long head hair). Possibly this occurred in conjunction with neoteny, with the more juvenile appearing females being selected by males as more desirable; see types of hair and vellus hair.

The aquatic ape hypothesis posits that sparsity of hair is an adaptation to an aquatic environment, but it has little support amongst scientists and very few aquatic mammals are, in fact, hairless.

In reality, there may be little to explain. Humans, like all primates, are part of a trend toward sparser hair in larger animals; the density of human hair follicles on the skin is actually about what one would expect for an animal of equivalent size[2]. The outstanding question is why so much of human hair is short, underpigmented vellus hair rather than terminal hair.

Head hair

Young Girl Fixing her Hair, by Sophie Gengembre Anderson

Head hair is a type of hair that is grown on the head (sometimes referring directly to the scalp)[citation needed].The most noticeable part of human hair is the hair on the head, which can grow longer than on most mammals and is more dense than most hair found elsewhere on the body. The average human head has about 100,000 hair follicles. [1] Its absence is termed alopecia, commonly known as baldness. Anthropologists speculate that the functional significance of long head hair may be adornment, a by-product of secondary natural selection once other somatic hair had been lost. Another possibility is that long head hair is a result of Fisherian runaway sexual selection, where long lustrous hair is a visible marker for a healthy individual (with good nutrition, waist length hair—approximately 1 meter or 39 inches long—would take around 84 months, or about 7 years, to grow). Each follicle can grow about 20 individual hairs in a person's lifetime. [2] Average hair loss is about 100 strands a day. The average human scalp measures approximately 120 square inches (770 cm²). These values are also reported by Desmond Morris[3] although it is not clear if these are applicable to both men and women.

Average number of head hairs (Caucasian) [3]

color number of hairs diameter
Blonde 146,000 11500th to 1500th inch 17 to 51 micrometers
Black 110,000 1400th to 1250th inch 64 to 100 micrometers
Brunette 100,000 variable variable
Red 86,000 variable variable
Traditional Hopi hair style, photo by Edward S. Curtis, 1922
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Traditional Hopi hair style, photo by Edward S. Curtis, 1922

Types of hair

Humans have three different types of hair:

  • Lanugo, the fine hair that covers nearly the entire body of fetuses
  • Vellus hair, the short, fine, "peach fuzz" body hair that grows in most places on the human body in both sexes
  • Terminal hair, the fully developed hair, which is generally longer, coarser, thicker, and darker than vellus hair.

Growth

Distribution of androgenic hair on female and male body
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Distribution of androgenic hair on female and male body

Different parts of the human body feature different types of hair. From childhood onward, vellus hair covers the entire human body regardless of sex or race except in the following locations: the lips, the palms of hands, the soles of feet, certain external genital areas, the navel and scar tissue. The density of the hairs (in hair follicles per square centimeter) varies from one person to another.

The rising level of male hormones (androgens) during puberty causes a transformation process of vellus hair into terminal hair on several parts of the body. The hair follicles respond to androgens, primarily testosterone and its derivatives; the hair in these locations can be thus termed androgenic hair. The rate of hair growth and the weight of the hairs increase. However, different areas respond with different sensitivities. As testosterone levels increase, the sequence of appearance of androgenic hair reflects the gradations of androgen sensitivity. The pubic area is most sensitive, and heavier hair usually grows there first in response to androgens.

Layers of an individual hair
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Layers of an individual hair

Areas on the human body that develop terminal hair growth due to rising androgens in both sexes, men and women, are the underarms and the pubic area. In contrast, normally only men grow androgenic hair in other areas. There is a sexual dimorphism in the amount and distribution of androgenic hair, with males having more terminal hair (particularly facial hair, chest hair, abdominal hair and hair on legs and arms) and females having more vellus hair, which is less visible. The genetic disposition determines the sex-dependent and individual rising of androgens and therefore the development of androgenic hair.

Increased body hair on women following the male pattern can be referred to as hirsutism. An excessive and abnormal hair growth on the body of males and females is defined as hypertrichosis. Considering an individual occurrence of body hair as abnormal does not implicitly depend on medical indications but also on cultural and social attitudes.

Individual hairs alternate periods of growth and dormancy. During the growth portion of the cycle, hair follicles are long and bulbous, and the hair advances outward at about a third of a millimeter per day. After three to six months, body hair growth stops (the pubic and armpit areas having the longest growth period). The follicle shrinks and the root of the hair grows rigid. Following a period of dormancy, another growth cycle starts, and eventually a new hair pushes the old one out of the follicle from beneath. Head hair, by comparison, grows for a long duration and to a great length before being shed. The rate of growth is approximately 15 millimeters, or about ⅝ inch, per month.

Photo of Statue with curly hair
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Photo of Statue with curly hair

Texture

Hair texture is measured by the degree of which one's hair is either fine or coarse, which in turn varies according to the diameter of each individual hair. There are usually four major types of hair texture: fine, medium, coarse and wiry. Within the four texture ranges hair can also be thin, medium or thick density and it can be straight, curly, wavy or kinky. Hair conditioner will also alter the ultimate equation and can be healthy, normal, oily, dry, damaged or a combination. Hair can also be textured if straighteners, crimpers, curlers, etc are used to style hair. Also, an expert hairdresser can change the hair texture with the use of special chemicals.

Hair is genetically programmed to be straight, curly or wavy, and it tends to change over time.

For many years, it was believed that the shape of a person’s hair was determined by the individual hair shafts, and that curly hair was curly because the cross-section of the hair shaft was flatter and had more intertwined layers than straight hair, which was round. But scientists have determined that whether your hair is curly or straight is determined by the shape of the follicle itself and the direction in which each strand grows out of its follicle. Curly hair is shaped like an elongated oval and grows at a sharp angle to the scalp.

Curly hair has a different biological structure than straight hair. It tends to be much drier than straight hair because the oils secreted into the hair shaft by the sebaceous glands can more easily travel down the shaft of straight hair. People with very curly hair may find that this hair type can be dry, hard to manage, and often frizzy.

Hair, whether it is curly or straight, is affected by the amount of humidity in the air. It serves as a "truth serum" for the hair, forcing water back into the hair fiber and forcing hair shaft to return to its original structure. This may be more noticeable in somebody with curly hair because it tends to get frizzy when the humidity rises.

Hair texture variation is likely to have resulted from a significant event in human evolutionary history. Evolutionary biologists agree that the evidence suggests that genus Homo arose in East Africa approximately 2 million years ago. During this time body size increased in response to richer dietary intake. This increase was most likely a reflection of rapidly increasing brain size among members of this genus, which facilitated an increasing intellectual capacity that made more varied dietary access possible (i.e. via new hunting and scavenging techniques etc.). Jablonski et al (2004) postulate that as body size increase, it became evolutionarily necessary to expel heat from the body at a more rapid rate. As a result, humans developed the ability to sweat. They also lost body hair in order to facilitate sweat evaporation and hence cooling of the body.

Aging

Older people tend to develop grey hair because the pigment in the hair is lost and the hair becomes colorless. Grey hair is considered to be a characteristic of normal aging. The age at which this occurs varies from person to person, but in general nearly everyone 75 years or older has grey hair, and in general men tend to become grey at younger ages than women.

It should be noted however, that grey hair in itself is not actually grey; the grey head of hair is a result of a combination of the dark and white/colorless hair forming an overall 'grey' appearance to the observer. As such, people starting out with very pale blond hair usually develop white hair instead of grey hair when aging. Red hair usually doesn't turn grey with age; rather it becomes a sandy color and afterward turns white. In fact, the grey or white appearance of individual hair fibers is a result of light scattering from air bubbles in the central medula of the hair fiber. Some degree of scalp hair loss or thinning generally accompanies aging in both males and females, and it's estimated that half of all men are affected by male pattern baldness by the time they are 50[4]. The tendency toward baldness is a trait shared by a number of other primate species, and is thought to have evolutionary roots.

It is commonly claimed that hair and nails will continue growing for several days after death. This is a myth; the appearance of growth is actually caused by the retraction of skin as the surrounding tissue dehydrates, making nails and hair more prominent.

Pathological impacts on hair

Drugs used in cancer chemotherapy frequently cause a temporary loss of hair, noticeable on the head and eyebrows, because they kill all rapidly dividing cells, not just the cancerous ones. Other diseases and traumas can cause temporary or permanent loss of hair, either generally or in patches.

The hair shafts may also store certain poisons for years, even decades, after death. In the case of Col. Lafayette Baker, who died July 3, 1868, use of an atomic absorption spectrophotometer showed the man was killed by white arsenic. The prime suspect was Wally Pollack, Baker's brother-in-law. According to Dr. Ray A. Neff, Pollack had laced Baker's beer with it over a period of months, and a century or so later minute traces of arsenic showed up in the dead man's hair. Mrs. Baker's diary seems to confirm that it was indeed arsenic, as she writes of how she found some vials of it inside her brother's suitcoat one day.

Width

According to The Physics Factbook, the diameter of human hair ranges from 17 to 181 µm.[4]

Cultural attitudes

Head hair

People from different cultures have invented various ways to arrange, or "style" their hair.
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People from different cultures have invented various ways to arrange, or "style" their hair.

The remarkable head hair of humans has gained an important significance in nearly all present societies as well as any given historical period throughout the world. The haircut has always played a significant cultural and social role.

In ancient Egypt head hair was often shaved, especially amongst children, as long hair was uncomfortable in the heat. Children were often left with a long lock of hair growing from one part of their heads, the practice being so common that it became the standard in Egyptian art for artists to depict children as always wearing this "sidelock". Many adult men and women kept their heads permanently shaved for comfort in the heat and to keep the head free of lice, while wearing a wig in public.

In ancient Greece and ancient Rome men and women already differed from each other through their haircuts. The head hair of women was long and pulled back into a chignon. Many dyed their hair red with henna and sprinkled it with gold powder, often adorning it with fresh flowers. Men’s hair was short and even occasionally shaved. In Rome hairdressing became ever more popular and the upper classes were attended to by slaves or visited public barber shops.

Maasai warriors with their traditional hair styling
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Maasai warriors with their traditional hair styling


The traditional hair styling in some parts of Africa also gives interesting examples of how people dealt with their head hair. The Maasai warriors tied the front hair into sections of tiny braids while the back hair was allowed to grow to waist length. Women and non-warriors, however, shaved their heads. Many tribes dyed the hair with red earth and grease; some stiffened it with animal dung.

Contemporary social and cultural conditions have constantly influenced popular hair styles. From the 17th century into the early 19th century it was the norm in Western culture for men to have long hair often tied back into a ponytail. Famous long-haired men include René Descartes, Giacomo Casanova, Oliver Cromwell and George Washington. During his younger years Napoleon Bonaparte had a long and flamboyant head of hair. Before World War I men generally had longer hair and beards. The trench warfare between 1914 and 1918 exposed men to lice and flea infestations, which prompted the order to cut hair short, establishing a norm that has persisted.

It has also been advanced that short hair on men has been enforced as a means of control, as shown in the military and police and other forces that require obedience and discipline. Additionally, slaves and defeated armies were often required to shave their heads, in both pre-medieval Europe and China.

Long hair was almost universal among women in Western culture until World War I. Many women in conservative Pentecostal groups abstain from trimming their hair after conversion (and some have never had their hair trimmed or cut at all since birth). The social revolution of the 1960s led to a renaissance of unchecked hair growth. Hair length is measured from the front scalp line on the forehead up over the top of the head and down the back to the floor. Standard milestones in this process of hair growing are waist length, hip length, classic length (midpoint on the body, where the buttocks meet the thighs), thigh length, knee length, ankle length and even beyond. It takes about seven years, including occasional trims, to grow one's hair to waist length. Terminal length varies from person to person according to genetics and overall health.

A thriving salon culture in Detroit gave rise to the Detroit Hair Wars in 1991. Using the medium of human and synthetic hair, elaborate fantastical head pieces, such as spider webs, flowers and flying "hair-y copters", have been made by participants.[5]

Body hair

Mark Twain, Shirtless. A human male with body hair.
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Mark Twain, Shirtless. A human male with body hair.

The attitudes towards hair on the human body also vary between different cultures and times. In some cultures profuse chest hair on men is a symbol of virility and masculinity; other societies display a hairless body as a sign of youthfulness.

In ancient Egypt, people regarded a completely smooth, hairless body as the standard of beauty. An upper class Egyptian woman took great pains to ensure that she did not have a single hair on her body, except for the top of her head (and even this was often replaced with a wig[5]). The ancient Greeks later adopted this smooth ideal, considering a hairless body to be representative of youth and beauty. This is reflected in Greek female sculptures which do not display any pubic hair. Islam stipulates many tenets with respect to hair, such as the covering of hair by women and the removal of armpit and pubic hair (see five physical characteristics traits of fitrah).

In Western societies it became a public trend during the late twentieth century, particularly for women, to reduce or to remove their body hair. The bikini and Brazilian waxing fashion as well as the sexual imagery in advertising and movies are major reasons for this development. This media trend began in the United States and is becoming ever more popular throughout other Western countries. It was also beginning to gain currency among men, among whom shaving or trimming one's body hair is sometimes jokingly called "manscaping".[citations needed]

Hair as business factor

Hair care for humans is a major world industry with specialized tools, chemicals and techniques. The business of various products connected with human hair has become an important industrial and financial factor in Western societies.

Social role of hair

Hair has great social significance for human beings. It can grow on most areas of the human body, except on the palms of the hands and the soles of the feet (among other areas), but hair is most noticeable in most people in a small number of areas, which are also the ones that are most commonly trimmed, plucked, or shaved. These include the face, nose, ears, head, eyebrows, eyelashes, legs and armpits, as well as the pubic region.

The highly visible differences between male and female body and facial hair are a notable secondary sex characteristic.

Hair has had social and sexual significance in a number of societies, as a sign of masculinity in men, and femininity in women when in the "right" place, and as a sign of effeminacy in men and unfemininity in women when in the "wrong" place. Where the right and wrong places are differs from one culture to another.