What is the growth rate for human hair?
Isotope analysis
A recent development in forensic science is the isotopic analysis of hair strands. Hair has a recognisable growth rate of 9-11mm per month or 15 cm per year. Human hair growth is primarily a function of diet, especially drinking water intake. The stable isotopic ratios of drinking water are a function of location, and the geology that the water percolates through. Sr, Sr and oxygen isotope variations are different all over the world. These differences in isotopic ratio are then biologically 'set' in our hair as it grows and it has therefore become possible to identify recent geographic histories by the analysis of hair strands. For example, it could be possible to identify whether a terrorist suspect had recently been to a particular location from hair analysis. This hair analysis is a non-invasive method which is becoming very popular in cases that DNA or other traditional means are bringing no answers.
Human evolutionary genetics
A gene for type I hair keratin was lost in the human lineage. Keratins are a major component of hairs. Humans still have nine functional type I hair keratin genes, but the loss of that particular gene may have caused the thinning of human body hair. Based on the assumption of a constant molecular clock, the study predicts the gene loss occurred relatively recently in human evolution—less than 240 000 years ago, but both the Vindija Neandertal and the high-coverage Denisovan sequence contain the same premature stop codons as modern humans and hence dating should be greater than 750 000 years ago. 
Stedman "et al." (2004) stated that the loss of the sarcomeric myosin gene MYH16 in the human lineage led to smaller masticatory muscles. They estimated that the mutation that led to the inactivation (a two base pair deletion) occurred 2.4 million years ago, predating the appearance of "Homo ergaster/erectus" in Africa. The period that followed was marked by a strong increase in cranial capacity, promoting speculation that the loss of the gene may have removed an evolutionary constraint on brain size in the genus "Homo".
Pattern hair loss
Pattern hair loss, known as male-pattern hair loss (MPHL) when it affects males and female-pattern hair loss (FPHL) when it affects females, is hair loss that primarily affects the top and front of the scalp. In males, the hair loss often presents as a receding hairline, while in females, it typically presents as a thinning of the hair.
Male pattern hair loss is believed to be due to a combination of genetics and the male hormone dihydrotestosterone. The cause in female pattern hair loss remains unclear.
Management may include simply accepting the condition. Otherwise, treatments may include minoxidil, finasteride, or hair transplant surgery. Evidence for finasteride in women, however, is poor and it may result in birth defects if taken during pregnancy.
Pattern hair loss by the age of 50 affects about half of males and a quarter of females. It is the most common cause of hair loss. 
Classic male-pattern hair loss begins above the temples and vertex (calvaria) of the scalp. As it progresses, a rim of hair at the sides and rear of the head remains. This has been referred to as a 'Hippocratic wreath', and rarely progresses to complete baldness. Pattern hair loss is classified as a form of non-scarring hair loss. The Hamilton–Norwood scale has been developed to grade androgenic alopecia in males.
Demographics of the world
Globally, the growth rate of the human population has been declining since peaking in 1962 and 1963 at 2.20% per annum. In 2009, the estimated annual growth rate was 1.1%. The CIA World Factbook gives the world annual birthrate, mortality rate, and growth rate as 1.915%, 0.812%, and 1.092% respectively The last one hundred years have seen a rapid increase in population due to medical advances and massive increase in agricultural productivity made possible by the Green Revolution.
The actual annual growth in the number of humans fell from its peak of 88.0 million in 1989, to a low of 73.9 million in 2003, after which it rose again to 75.2 million in 2006. Since then, annual growth has declined. In 2009, the human population increased by 74.6 million, which is projected to fall steadily to about 41 million per annum in 2050, at which time the population will have increased to about 9.2 billion. Each region of the globe has seen great reductions in growth rate in recent decades, though growth rates remain above 2% in some countries of the Middle East and Sub-Saharan Africa, and also in South Asia, Southeast Asia, and Latin America.
Long hair
Humans, horses, orangutans and lions are among the few species that may grow their head hair or manes very long. Humans are believed to have lost their fur 2.5–3 million years ago as hominids when transitioning from a forest habitat to the open savanna, as an effect of natural selection, since this development made it possible to run fast and hunt animals close to the equator without getting overheated. An exception was however head hair, which was kept to provide thermal insulation of the scalp from the sun, to protect against ultra-violet radiation exposure, and also to provide cooling (when sweat evaporates from soaked hair). The ability to grow straight hair has been observed among Homo sapiens sub-groups in less sunny regions further away from the equator. Relative to kinked Afro-textured hair, straight hair allows more UV light to pass to the scalp (which is essential for the production of vitamin D, that is important for bone development).
Human hair color
Changes in hair color typically occur naturally as people age, eventually turning the hair gray and then white. This is called achromotrichia. Achromotrichia normally begins in the early to mid-twenties in men and late twenties in women. More than 60 percent of Americans have some gray hair by age 40. The age at which graying begins seems almost entirely due to genetics. Sometimes people are born with gray hair because they inherit the trait.
Follicular unit transplantation
Follicular Unit Transplantation enables the hair transplant to look natural both at the individual follicular unit level and in regards to the overall graft distribution. Since scalp hair normally grows in follicular units of 1 to 4 hairs, the exclusive use of these naturally-occurring units in FUT ensures that each graft will be identical to the surrounding follicular units. Thus, when the transplanted follicular units grow hair after a transplant, the overall results of the transplant will appear natural.
Hair theft
Hair theft has been a recurrent problem in various parts of the world where human hair is in demand either for commercial products such as wigs and hairpieces, or for sexual fetishes. As hair has a high commercial value – in the mid-19th century it was regarded as worth twice its weight in silver – opportunist thieves have targeted long-haired women, and less commonly men and children, with the aim of stealing their hair. Hair thieves have typically sought either to surreptitiously cut off hair in public places, or have mugged people and shorn their heads. The crime of hair theft has been widely reported in North America, Europe, Asia and Australasia over the course of at least 300 years.
Human evolutionary developmental biology
Jeremy De Silva and Julie Lesnik examined chimpanzee neonatal brain size to identify implications for brain growth in "Homo erectus". This changed the understanding of differences and similarities of post-natal brain growth in humans and chimpanzees. The study found that there was a distinction necessary between growth time and growth rate.The times of growth were strikingly similar, but the rates were not. The paper further advocates the use of fossils to assess brain size in general and in relation to cranial capacity.
Human hair color
Red hair ranges from light strawberry blond shades to titian, copper, and completely red. It is caused by a variation in the "Mc1r" gene and is recessive. Red hair has the highest amounts of pheomelanin, around 67%, and usually low levels of eumelanin. At 1–2% of the population, it is the least common hair color in the world. It is most prominently found in the British Isles. Scotland has the highest proportion of redheads; 13 percent of the population has red hair and approximately 40 percent carry the recessive redhead gene.
Drug test
However, there is one major difference between most drugs and alcohol metabolites in the way in which they enter into the hair: on the one hand like other drugs FAEEs enter into the hair via the keratinocytes, the cells responsible for hair growth. These cells form the hair in the root and then grow through the skin surface taking any substances with them. On the other hand, the sebaceous glands produce FAEEs in the scalp and these migrate together with the sebum along the hair shaft (Auwärter et al., 2001, Pragst et al., 2004). So these glands lubricate not only the part of the hair that is just growing at 0.3 mm per day on the skin surface, but also the more mature hair growth, providing it with a protective layer of fat.
Fur
Humans are the only primate species that have undergone significant hair loss. The hairlessness of humans compared to related species may be due to loss of functionality in the pseudogene KRTHAP1 (which helps produce keratin) in the human lineage about 240,000 years ago. Mutations in the gene HR can lead to complete hair loss, though this is not typical in humans.
Human
In developed countries, infants are typically in weight and in height at birth. However, low birth weight is common in developing countries, and contributes to the high levels of infant mortality in these regions. Helpless at birth, humans continue to grow for some years, typically reaching sexual maturity at 12 to 15 years of age. Females continue to develop physically until around the age of 18, whereas male development continues until around age 21. The human life span can be split into a number of stages: infancy, childhood, adolescence, young adulthood, adulthood and old age. The lengths of these stages, however, have varied across cultures and time periods. Compared to other primates, humans experience an unusually rapid growth spurt during adolescence, where the body grows 25% in size. Chimpanzees, for example, grow only 14%, with no pronounced spurt. The presence of the growth spurt is probably necessary to keep children physically small until they are psychologically mature. Humans are one of the few species in which females undergo menopause. It has been proposed that menopause increases a woman's overall reproductive success by allowing her to invest more time and resources in her existing offspring, and in turn their children (the grandmother hypothesis), rather than by continuing to bear children into old age.
Abdominal hair
Before puberty, the abdominal region of both males and females is covered with very fine vellus hair. In response to rising levels of androgens (mainly testosterone) during and after puberty, the skin of the abdomen begins to produce coarser, longer and more pigmented hair (terminal hair). This process primarily affects men. Initially hair grows in a vertical line from the pubic area up to the navel and from the thorax down to the navel. Slang terms for this line of hair include "goodie trail", "snail trail", "tiger line", or "treasure trail". Although the development of abdominal hair normally begins during puberty, it may also start later, between the ages of 20 and 30. With some men, the abdominal hair will stay within a clearly defined vertical line, but in others, terminal hair will appear laterally as well as vertically, particularly in the area around the navel. This lateral spreading can continue into middle age.
Body hair
Terminal hair growth on arms is a secondary sexual characteristic in boys and appears in the last stages of puberty. Vellus arm hair is usually concentrated on the elbow end of the forearm and often ends on the lower part of the upper arm. This type of intense arm vellus hair growth sometimes occurs in young women and people of both sexes until puberty. Even though this causes the arms to appear hairy, it is not caused solely by testosterone. The hair is softer and different from men's arm hair, in texture.
Human hair growth
At some point, the follicle will begin to grow again, softening the anchor point of the shaft initially. The hair base will break free from the root and the hair will be shed. Within two weeks the new hair shaft will begin to emerge once the telogen phase is complete. The process results in normal hair loss known as shedding.
Hair ice
Hair ice (also known as ice wool or frost beard) is a type of ice that forms on dead wood and takes the shape of fine, silky hair. It is somewhat uncommon, and has been reported mostly at latitudes between 45–55 °N in broadleaf forests. The meteorologist and discoverer of continental drift, Alfred Wegener, described hair ice on wet dead wood in 1918, assuming some specific fungi as the catalyst, a theory mostly confirmed by Gerhart Wagner and Christian Mätzler in 2005. In 2015, the fungus "Exidiopsis effusa" was identified as key to the formation of hair ice.
Hair
Another hypothesis for the thick body hair on humans proposes that Fisherian runaway sexual selection played a role (as well as in the selection of long head hair), (see types of hair and vellus hair), as well as a much larger role of testosterone in men. Sexual selection is the only theory thus far that explains the sexual dimorphism seen in the hair patterns of men and women. On average, men have more body hair than women. Males have more terminal hair, especially on the face, chest, abdomen, and back, and females have more vellus hair, which is less visible. The halting of hair development at a juvenile stage, vellus hair, would also be consistent with the neoteny evident in humans, especially in females, and thus they could have occurred at the same time. This theory, however, has significant holdings in today's cultural norms. There is no evidence that sexual selection would proceed to such a drastic extent over a million years ago when a full, lush coat of hair would most likely indicate health and would therefore be more likely to be selected "for", not against, and not all human populations today have sexual dimorphism in body hair.
Human hair color
Europeans often begin to grow gray hairs in their mid-30s while Asians begin graying in their late 30s, but most Africans retain their original hair color until their mid-40s.
Cass Ole
His mane as seen in the two movies was partially enhanced. Like many American horses, Cass Ole had his mane trimmed into a bridle path. While he did have a long mane typical for his breed, its natural length was about equal to the width of his neck, which is the average maximum length that a horse's mane will grow when not specially groomed. Therefore, to hide his bridle path trimming and to create the long flowing mane that was seen in the movie itself, hair extensions were stitched into his mane to provide a fuller and longer look on camera. To grow a mane past its natural length requires it to be kept in braids, regularly conditioned, takes at least a year's time to achieve significant length, and, like humans, some horses' manes simply will not grow beyond a certain length.
Leg hair
Leg hair is hair that grows on the legs of humans, generally appearing after the onset of puberty. For hygienic or aesthetic reasons and for some sports, people shave, wax, or use hair removal creams to remove the hair from their legs: see leg shaving.
Red hair
Emigration from Europe has multiplied the population of red haired humans in the Americas, Australia, New Zealand and South Africa. In the United States, it is estimated that 2–6% of the population has red hair. This would give the U.S. the largest population of redheads in the world, at 6 to 18 million, compared to approximately 420,000 in Ireland and 300,000 in Scotland.
Long hair
Hair usually takes about two years to reach shoulder length, and about seven years to reach waist-length/hip-length, including occasional trims (approximately 80–90 cm (32–36 inches) from forehead for most people)
Human hair color
In non-balding individuals hair may grow faster once it turns gray.
Psychemedics Corporation
After years of research proved that drugs deposited in the hair can be accurately measured, the company was formed in 1987 and pioneered the use of hair testing in commercial markets including banks, manufacturers, retailers, mining operations, hotels and casinos. The technology capitalizes on the way the body metabolizes ingested drugs as they flow through the blood stream and deposit in the cortex of the hair. Hair is stable and the deposits are permanently embedded in the hair, so hair acts like a tape recorder — “recording” drug deposits in proportion to use over time as drugs are deposited in proportion to use. Hair grows at approximately the rate of ½ an inch per month and takes about 5 days to grow out past the external layer of skin. Psychemedics’ standard test uses a 1 ½ inch sample of head hair, which provides an approximate 3 month history of drug use. Body hair can also be collected if head hair is not available.
Hair
A group of studies have recently shown that genetic patterns at the EDAR locus, a region of the modern human genome that contributes to hair texture variation among most individuals of East Asian descent, support the hypothesis that (East Asian) straight hair likely developed in this branch of the modern human lineage subsequent to the original expression of tightly coiled natural afro-hair. Specifically, the relevant findings indicate that the EDAR mutation coding for the predominant East Asian 'coarse' or thick, straight hair texture arose within the past ≈65,000 years, which is a time frame that covers from the earliest of the 'Out of Africa' migrations up to now.
Hypertrichosis
Another mechanism involves a change in the hair cycle. There are three stages of the hair cycle: the anagen phase (hair growth), the catagen phase (hair follicle death), and the telogen phase (hair shedding). If the anagen phase increases beyond what is normal, that region of the body will experience excessive hair growth.
Knemometry
Short-term growth consists of small growth spurts (mini growth spurts). In the human neonate, these spurts occur at intervals of 2 to 10 days, and they reach maximum velocities of up to 0.2 mm per hour at the lower leg. Growth hormone therapies have been shown to significantly alter the dynamics of short-term growth. Catch-up growth (compensatory growth after periods of growth impairment due to illness, starvation and other unfavourable conditions) is characterised by repetitive series of broadened mini growth spurts.
Human hair growth
The protein called profis makes up hair and stimulates hair growth.
Body hair
P.E. Wheeler of the Department of Biology at Liverpool Polytechnic said quadrupedal savannah mammals of similar volume to humans have body hair to keep warm while only larger quadrupedal savannah mammals lack body hair, because their body volume itself is enough to keep them warm. Therefore, Wheeler said humans who should have body hair based on predictions of body volume alone for savannah mammals evolved no body hair after evolving bipedalism which he said reduced the amount of body area exposed to the sun by 40%, reducing the solar warming effect on the human body.
Melanocortin 1 receptor
In the United States, about 25% of the population carries the mutated melanocortin 1 receptor that causes red hair. With one in four people as carriers, the chance of two people having a child with red hair is about 2% (one in 64). The prevalence of red hair varies considerably worldwide. People with freckles and no red hair have an 85% chance of carrying the "MC1R" gene that is connected to red hair. People with no freckles and no red hair have an 18% chance of carrying the "MC1R" gene linked to red hair. Eight genes have been identified in humans that control whether the MC1R gene is turned on and the person has red hair.
Hair care
There are various reasons for hair loss, most commonly hormonal issues. Fluctuations in hormones will often show in the hair. Not all hair loss is related to what is known as male pattern baldness, women can suffer from baldness just as men do. Formulas for addressing this specific cause of lack of hair growth yet typically they require around three months of consistent use for results to begin to appear. Cessation may also mean that gained growth may dissipate.
Human hair growth
Traction alopecia is caused by adding too much strain on the hair on one's head. Tight ponytails and other styles that require added tension to the hair are often what cause this disease. It can also occur on the face in areas where the hair is often styled. Plucking or waxing one's eyebrows frequently, for example, can yield suppressed hair growth in the area.
Hair
Hair growth begins inside the hair follicle. The only "living" portion of the hair is found in the follicle. The hair that is visible is the hair shaft, which exhibits no biochemical activity and is considered "dead". The base of a hair's root (the "bulb") contains the cells that produce the hair shaft. Other structures of the hair follicle include the oil producing sebaceous gland which lubricates the hair and the arrector pili muscles, which are responsible for causing hairs to stand up. In humans with little body hair, the effect results in goose bumps.
Beard
A beard is the collection of hair that grows on the chin, upper lip, cheeks and neck of humans and some non-human animals. In humans, usually only pubescent or adult males are able to grow beards. However, women with hirsutism, a hormonal condition of excessive hairiness, may develop a beard.
Body hair
Hair follicles are to varying degrees sensitive to androgen, primarily testosterone and its derivatives, particularly dihydrotestosterone, with different areas on the body having different sensitivity. As androgen levels increase, the rate of hair growth and the weight of the hairs increase. Genetic factors determine both individual levels of androgen and the hair follicle's sensitivity to androgen, as well as other characteristics such as hair colour, type of hair and hair retention.
Adolescence
Facial hair in males normally appears in a specific order during puberty: The first facial hair to appear tends to grow at the corners of the upper lip, typically between 14 and 17 years of age. It then spreads to form a moustache over the entire upper lip. This is followed by the appearance of hair on the upper part of the cheeks, and the area under the lower lip. The hair eventually spreads to the sides and lower border of the chin, and the rest of the lower face to form a full beard. As with most human biological processes, this specific order may vary among some individuals. Facial hair is often present in late adolescence, around ages 17 and 18, but may not appear until significantly later. Some men do not develop full facial hair for 10 years after puberty. Facial hair continues to get coarser, darker and thicker for another 2–4 years after puberty.
Hair loss
Normally, about 40 (0–78 in men) hairs reach the end of their resting phase each day and fall out. When more than 100 hairs fall out per day, clinical hair loss (telogen effluvium) may occur. A disruption of the growing phase causes abnormal loss of anagen hairs (anagen effluvium).
Human height
Growth in stature, determined by its various factors, results from the lengthening of bones via cellular divisions chiefly regulated by somatotropin (human growth hormone (hGH)) secreted by the anterior pituitary gland. Somatotropin also stimulates the release of another growth inducing hormone Insulin-like growth factor 1 (IGF-1) mainly by the liver. Both hormones operate on most tissues of the body, have many other functions, and continue to be secreted throughout life; with peak levels coinciding with peak growth velocity, and gradually subsiding with age after adolescence. The bulk of secretion occurs in bursts (especially for adolescents) with the largest during sleep.
Hair care
Hair care is an overall term for hygiene and cosmetology involving the hair which grows from the human scalp, and to a lesser extent facial, pubic and other body hair. Hair care routines differ according to an individual's culture and the physical characteristics of one's hair. Hair may be colored, trimmed, shaved, plucked or otherwise removed with treatments such as waxing, sugaring and threading. Hair care services are offered in salons, barbershops and day spas, and products are available commercially for home use. Laser hair removal and electrolysis are also available, though these are provided (in the US) by licensed professionals in medical offices or speciality spas.
Human hair color
Children born with some hair colors may find it gradually darkens as they grow. Many blond, light brown, or red haired infants experience this. This is caused by genes being turned off and on during early childhood and puberty.
Nail (anatomy)
In humans, nails grow at an average rate of a month. Fingernails require three to six months to regrow completely, and toenails require twelve to eighteen months. Actual growth rate is dependent upon age, sex, season, exercise level, diet, and hereditary factors. 
The longest female nails known ever to have existed measured a total of 601.9 cm, an average of 60.19 cm (23.7 inches) for each fingernail. Contrary to popular belief, nails do not continue to grow after death; the skin dehydrates and tightens, making the nails (and hair) appear to grow.
Human hair growth
UV levels of either 20 or 50 mJ cm in the UV-B range have been shown to inhibit hair growth, reduce hair melanin and damage hair follicles.
Human brain
As a hominid brain, the human brain is substantially enlarged even in comparison to the brain of a typical monkey. The sequence of human evolution from "Australopithecus" (four million years ago) to "Homo sapiens" (modern humans) was marked by a steady increase in brain size. As brain size increased, this altered the size and shape of the skull, from about 600 cm in "Homo habilis" to an average of about 1520 cm in "Homo neanderthalensis". Differences in DNA, gene expression, and gene–environment interactions help explain the differences between the function of the human brain and other primates.
Hair
Further, it is notable that the most pervasive expression of this hair texture can be found in sub-Saharan Africa; a region of the world that abundant genetic and paleo-anthropological evidence suggests, was the relatively recent (≈200,000-year-old) point of origin for modern humanity. In fact, although genetic findings (Tishkoff, 2009) suggest that sub-Saharan Africans are the most genetically diverse continental group on Earth, Afro-textured hair approaches ubiquity in this region. This points to a strong, long-term selective pressure that, in stark contrast to most other regions of the genomes of sub-Saharan groups, left little room for genetic variation at the determining loci. Such a pattern, again, does not seem to support human sexual aesthetics as being the sole or primary cause of this distribution.
Projections of population growth
The world population is currently growing by approximately 83 million people each year. Growth rates are slowing to various extents within different populations with result of the overall population growth rate decreasing from 1.55% per year in 1995 to 1.25% in 2005, 1.18% in 2015 and 1.10% in 2017. The median estimate for future growth sees the world population reaching 8.6 billion in 2030, 9.8 billion in 2050 and 11.2 billion by 2100 assuming a continuing decrease in average fertility rate from 2.5 births per woman in 2010–2015 to 2.2 in 2045–2050 and to 2.0 in 2095–2100, according to the medium-variant projection. With longevity trending towards uniform and stable values worldwide, the main driver of future population growth is the evolution of the fertility rate.
Big hair
Many people of various ethnicities throughout the world have naturally voluminous hair. For these people, "big hair" is not a deliberate fashion statement requiring any particular technique to achieve, but rather the default state of their hair. Some 60 percent of the world's population has naturally curly hair, which tends to be more voluminous than straight hair.
Chest hair
Chest hair is hair that grows on the chest of a person in the region between the neck and the abdomen. Chest hair develops during and after puberty along with other types of androgenic hair.
Hair's breadth
This measurement is not a precise one. Human hair varies in diameter, ranging anywhere from 17 μm to 181 μm. One nominal value often chosen is 75 μm, but this – like other measures based upon such highly variant natural objects, including the barleycorn – is subject to a fair degree of imprecision.
Long hair
1972, it was estimated that 24% of American women wore shoulder length hair or longer (44% of women in ages 14 to 44), meaning slightly more than 12% of men and women altogether. Similar frequency was found in 2001, when it was estimated that about 13% of the US adult population, male as well as females, has hair shoulder-length or longer, about 2.4% have hair reaching to the bottom of the shoulder blades or longer, about 0.3% have hair waist length or longer, and only about 0.017% have hair buttocks-length or longer. By extrapolating the above data and the number of hair length records, the number of people with shoulder-length hair or longer in the USA is estimated to be 27 million, those with waist-length hair roughly 900,000, those with buttocks-length hair to be 40,000, with knee length hair to 2,000 and with ankle length hair to 70.
Body hair
Facial hair, as the name suggests, grows primarily on or around one's face. Both men and women experience facial hair growth. Like pubic hair, non-vellus facial hair will begin to grow in around puberty. Moustaches in young men usually begin to grow in at around the age of puberty, although some men may not grow a moustache until they reach late teens or at all. For some cases facial hair development may take longer to mature than in the late teens but a lot of men experience no facial development even at an older age. Facial hair development has often been associated with stress levels.
Human hair growth
On the scalp, the hair is usually known to be lost around the hair line, leaving the densest amount of hair at the crown. Small vellus hair will often replace the hair that is lost.
Long hair
The maximum terminal hair length depends on the length of the anagen (period of hair growth) for the individual. Waist-length hair or longer is only possible to reach for people with long anagen. The anagen lasts between 2 and 7 years, for some individuals even longer, and is followed by shorter catagen (transition) and telogen (resting) periods. At any given time, about 85% of hair strands are in anagen. The fibroblast growth factor 5 (FGF5) gene affects the hair cycle in mammals including humans; blocking FGF5 in the human scalp (by applying a herbal extract that blocked FGF5) extends the hair cycle, resulting in less hair fall and increased hair growth.
Hair
The world's longest documented hair belongs to Xie Qiuping (China), at 5.627 m (18 ft 5.54 in) when measured on 8 May 2004. She has been growing her hair since 1973, from the age of 13.
Ingrown hair
Ingrown hair is a condition where a hair curls back or grows sideways into the skin. The condition is most prevalent among people who have coarse or curly hair. It may or may not be accompanied by an infection of the hair follicle (folliculitis) or "razor bumps" (pseudofolliculitis barbae), which vary in size. While ingrown hair most commonly appears in areas where the skin is shaved or waxed (beard, legs, pubic region), it can appear anywhere. Anything which causes the hair to be broken off unevenly with a sharp tip can cause ingrown hairs. Ingrown hairs are also caused because of lack of natural exfoliation in the skin.
Hair
Hair has great social significance for human beings.
Human hair color
Chestnut hair is a hair color which is a reddish shade of brown hair. In contrast to auburn hair, the reddish shade of chestnut is darker. Chestnut hair is common among the native peoples of Northern, Central, Western, and Eastern Europe.
Bolognese dog
The Bolognese often appears on lists of dogs that allegedly do not shed (moult). It is true that these dogs do not seasonally moult or lose large amounts of fur as many other breeds do. However, they do eventually lose and replace individual hairs, similar to human hair growth cycles. Each hair grows from a hair follicle, which has a three phase cycle, as do most mammals. These cycles are: "anagen", growth of normal hair; "catagen" growth slows, and hair shaft thins; "telegen", hair growth stops, follicle rests, and old hair fall off—is shed. At the end of the telegen phase, the follicle begins the cycle again. The length of time of the growing and shedding cycle varies by age and other factors. There is no such thing as a completely non-shedding breed.
Human hair color
Brown hair is characterized by higher levels of eumelanin and lower levels of pheomelanin. Of the two types of eumelanin (black and brown), brown-haired people have brown eumelanin; they also usually have medium-thick strands of hair. Brown-haired girls or women are often known as brunette.
Hair care
During pregnancy and breast feeding, the normal and natural shedding process is typically suspended (starting around month three because it takes a while for the body to recognize and reset for the hormonal shifts the body goes through) for the period of gestation and extended longer if one breast feeds (this includes pumping for breast milk). Upon cessation of either of these, it typically takes around two months for the hormones to shift again to the normal hormonal settings, and hair shedding can increase exponentially, for approximately 3–6 months until hair returns to its normal volume. It is commonly noticed that hair seems thicker and shinier, even, during pregnancy and breast feeding in response to the influx of shifting hormones. It is not unusual also for hair color to change, or hair structure to change (e.g., straighter hair, curlier hair). These changes can occur more often than people may realize yet isn't often reported.
Leg hair
It is said that hair growth occurs during the "growing" phase of the follicle, and then retained as dead club hair during the "resting" phase. The old club hair might be lost within the following "growing" phase.
Leg hair
Seasonal changes are also known to affect hair growth. For instance, one experiment had concluded that the rate of hair growth for men and their beards was lowest in January and February and increased from March to July.
Nudity
Hair probably evolved in mammals before about 220 million years ago. The closest living genetic relatives of humans, apes and especially chimpanzees, possess an almost complete covering of fur.
Hair
Hair grows everywhere on the external body except for mucus membranes and glabrous skin, such as that found on the palms of the hands, soles of the feet, and lips.
Vellus hair
Vellus hair is short, thin, slight-colored, and barely noticeable thin hair that develops on most of a person's body during childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital areas, the navel, and scar tissue. The density of hair – the number of hair follicles per area of skin – varies from person to person. Each strand of vellus hair is usually less than 2 mm (1/13 inch) long and the follicle is not connected to a sebaceous gland.
Human hair growth
Most chemotherapy drugs work by attacking rapidly dividing cells. Rapid cell replication is one of the hallmarks of cancer; however, hair follicle cells also grow and divide quickly. Consequently, the chemotherapy drugs usually inhibit hair growth. The dose and type of medicine will determine the severity of hair loss. Once the course of chemotherapy has ended, new hair growth may begin after three to 10 weeks.
Red hair
In Ireland, the percentage of population with red hair is estimated to be at around 10%, making it the world's highest concentrated population of red heads. According to IrelandsDNA, 34.7% of the Irish population carry the allele for red hair, although this doesn't directly translate proportionally into births of red-haired children.
Body Bags (film)
Richard Coberts is a middle-aged businessman who is very self-conscious about his thinning hair. This obsession has caused a rift between him and his long-suffering girlfriend Megan. Richard answers a television ad about a "miracle" hair transplant procedure, pays a visit to the office, and meets the shady Dr. Lock, who agrees to give Richard a solution to make his hair grow back. The next day, Richard wakes up and removes the bandage around his head, and is overjoyed to find that he has a full head of hair. But soon he becomes increasingly sick and fatigued, and finds his hair continuing to grow and, additionally, growing out of parts of his body, where hair does not normally grow. Trying to cut a hair off his mouth, he finds that it "screams", and, examining it under a magnifying glass, sees that it's alive and resembles a tiny serpent. He goes back to Dr. Lock for an explanation, but finds himself a prisoner as Dr. Lock explains that he and his entire staff are aliens from another planet, seeking out narcissistic human beings and planting seeds of "hair" to take over their bodies for consumption as part of their plan to spread their essence to Earth.
Puberty
In the months and years following the appearance of pubic hair, other areas of skin that respond to androgens may develop androgenic hair. The usual sequence is: underarm (axillary) hair, perianal hair, upper lip hair, sideburn (preauricular) hair, periareolar hair, and the beard area. As with most human biological processes, this specific order may vary among some individuals. Arm, leg, chest, abdominal, and back hair become heavier more gradually. There is a large range in amount of body hair among adult men, and significant differences in timing and quantity of hair growth among different racial groups. Facial hair is often present in late adolescence, but may not appear until significantly later. Facial hair will continue to get coarser, darker and thicker for another 2–4 years after puberty. Some men do not develop full facial hair for up to 10 years after the completion of puberty. Chest hair may appear during puberty or years after, though not all men develop it.
Hair removal
Many men in Western cultures shave their facial hair, so only a minority of men have a beard, even though fast-growing facial hair must be shaved daily to achieve a clean-shaven or hairless look. Some men shave because they cannot grow a "full" beard (generally defined as an even density from cheeks to neck), because their beard color is different from their scalp hair color, or because their facial hair grows in many directions, making a groomed look difficult. Some men shave because their beards are very coarse, causing itchiness and irritation. Some men grow a beard or moustache from time to time to change their appearance.
Red hair
Red hair (or ginger hair) occurs naturally in one to two percent of the human population, appearing with greater frequency (two to six percent) among people of northern or western European ancestry and lesser frequency in other populations. It is most common in individuals homozygous for a recessive allele on chromosome 16 that produces an altered version of the MC1R protein.
Hair theft
This created a highly profitable market in human hair, which was said in the mid-19th century to be worth twice its weight in silver. In 1851 of hair was imported from France to England with a value of £3,621 (£ today). "The Hairdressers' Journal" reported in May 1863 that a hundred tons of hair a year was being sold in Parisian markets. Not all hair was created equal; female hair from northern Italy and Spain was especially prized for its glossy blackness and curliness. It retailed at a price of 10–12 shillings per ounce (worth about £43/€50/$67 in 2013 prices), rising to £1 per ounce (about £87/€101/$136) for very long hair. A "hair harvest" was held annually in the poorer villages of Italy, where local girls sold their hair to wig-makers. One observer of a hair harvesting event reported seeing "several girls, sheared, one after the other like sheep, and as many more standing ready for the shears, with their caps in their hands, and their long hair combed out, and hanging down to their waists."
Human hair growth
The catagen phase, also known as the transitional phase, allows the follicle to, in a sense, renew itself. During this time, which lasts about two weeks, the hair follicle shrinks due to disintegration and the papilla detaches and "rests," cutting the hair strand off from its nourishing blood supply. Signals sent out by the body (that only selectively affect 1 percent of all hair of one's body at any given time) determine when the anagen phase ends and the catagen phase begins. The first sign of catagen is the cessation of melanin production in the hair bulb and apoptosis of follicular melanocytes. Ultimately, the follicle is 1/6 its original length, causing the hair shaft to be pushed upward. While hair is not growing during this phase, the length of the terminal fibers increase when the follicle pushes them upward.
Hair removal
Hair typically grows all over the human body. Hair can become more visible during and after puberty and men tend to have thicker, more visible body hair than women.
Both men and women have visible hair on the head, eyebrows, eyelashes, armpits, pubic region, arms, and legs; men and some women also have thicker hair on their face, abdomen, back and chest. Hair does not generally grow on the lips, the underside of the hands or feet or on certain areas of the genitalia.
Body hair
Visible hair appearing on the top surfaces of the feet and toes generally begins with the onset of puberty. Terminal hair growth on the feet is typically more intense in adult and adolescent males than in females.
Pattern hair loss
Transgenic studies have shown that growth and dormancy of hair follicles are related to the activity of insulin-like growth factor (IGF) at the dermal papillae, which is affected by DHT. Androgens are important in male sexual development around birth and at puberty. They regulate sebaceous glands, apocrine hair growth, and libido. With increasing age, androgens stimulate hair growth on the face, but can suppress it at the temples and scalp vertex, a condition that has been referred to as the 'androgen paradox'.
Sex differences in human physiology
Although men grow hair faster than women, baldness is much more common in males than in females. The main cause for this is "male pattern baldness" or androgenic alopecia. Male pattern baldness is a condition where hair starts to get lost in a typical pattern of receding hairline and hair thinning on the crown, and is caused by hormones and genetic predisposition.
Body hair
Loss of fur occurred at least 2 million years ago, but possibly as early as 3.3 million years ago judging from the divergence of head and pubic lice, and aided persistence hunting (the ability to catch prey in very long distance chases) in the warm savannas where hominins first evolved. The two main advantages are felt to be bipedal locomotion and greater thermal load dissipation capacity due to better sweating and less hair.
Long hair
In most current cultures, it is more typical for women to wear long hair than for men to do so. An American study shows significant correlation between hair length and age, which indicates that younger women tend to have longer hair than older women. A significant correlation was also found between women's hair length and hair quality. Moreover, hair quality was correlated with the women's perceived physical health. Consistent with principles of evolutionary psychology, these results indicate that hair length and quality can act as a cue to a woman's youth and health, signifying reproductive potential. The correlation between the woman's hair length and marital status, or number of children, was however not more than to be expected from the correlation between hair length and age.
Health impact of asbestos
Individual asbestos fibers are invisible to the unaided human eye because their size is about 3–20 µm wide and can be as slim as 0.01 µm. Human hair ranges in size from 17 to 181 µm in breadth. Fibers ultimately form because when these minerals originally cooled and crystallized, they formed by the polymeric molecules lining up parallel with each other and forming oriented crystal lattices. These crystals thus have three cleavage planes, and in this case, there are two cleavage planes which are much weaker than the third. When sufficient force is applied, they tend to break along their weakest directions, resulting in a linear fragmentation pattern and hence a fibrous form. This fracture process can keep occurring and one larger asbestos fiber can ultimately become the source of hundreds of much thinner and smaller fibers.
Hair follicle
The hair follicle is a dynamic organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between hormones, neuropeptides and immune cells. This complex interaction induces the hair follicle to produce different types of hair as seen on different parts of the body. For example, terminal hairs grow on the scalp and lanugo hairs are seen covering the bodies of fetuses in the uterus and in some new born babies. The process of hair growth occurs in distinct sequential stages. The first stage is called "anagen" and is the active growth phase, "catagen" is the resting stage, "telogen" is the regression of the hair follicle phase, "exogen" is the active shedding of hair phase and lastly "kenogen" is the phase between the empty hair follicle and the growth of new hair.
Drug test
Hair drug testing is a method that can detect drug use over a much longer period of time, and is often used for highly safety-critical positions where there is zero tolerance of illegal drug use. Standard hair follicle screen covers a period of 30 to 90 days. The growth of head hair is usually at the rate of 0.5 inches per month. The hair sample is cut close to the scalp and 80 to 120 strands of hair are needed for the test. In the absence of hair on the head, body hair can be used as an acceptable substitute. This includes facial hair, the underarms, arms, and legs or even pubic hair. Because body hair grows at a different rate than head hair, the timeframe changes, with scientists estimating that drug use can be detected in body hair for up to 12 months. Currently, most entities that use hair testing have prescribed consequences for individuals removing hair to avoid a hair drug test.
Hair whorl
A hair whorl is a patch of hair growing in a circular direction around a visible center point. Hair whorls occur in most hairy animals, on the body as well as on the head. Hair whorls, also known as crowns, swirls, or trichoglyphs, can be either clockwise or counterclockwise in direction of growth.
Hair fetishism
Hair is one of the defining characteristics of mammals. In humans, hair can be scalp hair, facial hair, chest hair, pubic hair, axillary hair, besides other places. Men tend to have hair in more places than women. Hair does not in itself have any intrinsic sexual value other than the attributes given to it by individuals in a cultural context. Some cultures are ambivalent in relation to body hair, with some being regarded as attractive while others being regarded as unaesthetic. Many cultures regard a woman's hair to be erotic. For example, many Islamic women cover their hair in public, and display it only to their family and close friends. Similarly, many Jewish women cover their hair after marriage. During the Middle Ages, European women were expected to cover their hair after they married, and according to the New Testament, a christian woman should cover her head while in a church or in prayer.
Underarm hair
Underarm hair, as human body hair, normally starts to appear at the beginning of puberty, with growth usually completed by the end of the teenage years.
Axillary hair goes through 4 stages of development, driven by weak androgens produced by the adrenal in males and females during adrenarche, and testosterone from the testicle in males during puberty. Like Tanner Staging for pubic hair, axillary hair can be staged according to the staging system, named for Pediatric Endocrinologist, , as follows:
Staging a patient's axillary hair will allow the physician to track the child's development longitudinally.
Let's trim our hair in accordance with the socialist lifestyle
It was broadcast on state-run Korean Central Television in the capital of Pyongyang and clips from the program were later rebroadcast on the British channel BBC One. The program claimed that hair length can affect human intelligence, in part because of the deprivation to the rest of the body of nutrients required for hair to grow. However, although some researchers have proposed that brain and hair are in competition from an evolutionary standpoint, cutting hair has no influence on its rate of growth. It was part of a longstanding North Korean government restriction campaign against haircuts and fashions deemed at odds with "Socialist values".
Hairdresser
Occupationally, hairdressing is expected to grow faster than the average for all other occupations, at 20%. A state license is required for hairdressers to practice, with qualifications varying from state to state. Generally a person interested in hairdressing must have a high school diploma or GED, be at least 16 years of age, and have graduated from a state-licensed barber or cosmetology school. Full-time programs often last 9 months or more, leading to an associate degree. After students graduate from a program, they take a state licensing exam, which often consists of a written test, and a practical test of styling or an oral exam. Hairdressers must pay for licenses, and occasionally licenses must be renewed. Some states allow hairdressers to work without obtaining a new license, while others require a new license. About 44% of hairdressers are self-employed, often putting in 40-hour work weeks, and even longer among the self-employed. In 2008, 29% of hairstylists worked part-time, and 14% had variable schedules. As of 2008, people working as hairdressers totaled about 630,700, with a projected increase to 757,700 by 2018.
Forensic toxicology
Hair is capable of recording medium to long-term or high dosage substance abuse. Chemicals in the bloodstream may be transferred to the growing hair and stored in the follicle, providing a rough timeline of drug intake events. Head hair grows at rate of approximately 1 to 1.5 cm a month, and so cross sections from different sections of the follicle can give estimates as to when a substance was ingested. Testing for drugs in hair is not standard throughout the population. The darker and coarser the hair the more drug that will be found in the hair. If two people consumed the same amount of drugs, the person with the darker and coarser hair will have more drug in their hair than the lighter haired person when tested. This raises issues of possible racial bias in substance tests with hair samples.
Hair
Shaving is accomplished with bladed instruments, such as razors. The blade is brought close to the skin and stroked over the hair in the desired area to cut the terminal hairs and leave the skin feeling smooth. Depending upon the rate of growth, one can begin to feel the hair growing back within hours of shaving. This is especially evident in men who develop a five o'clock shadow after having shaved their faces. This new growth is called stubble. Stubble typically appears to grow back thicker because the shaved hairs are blunted instead of tapered off at the end, although the hair never actually grows back thicker.
Facial hair
Great apes such as orangutan males seem to have facial hair as well. In chimpanzees and bonobos, facial and body hair become sparser in adulthood due to the aging process, which is in stark contrast to humans, whose facial and body hair become stronger. Because infant great apes have thicker "facial" (as well as body) hair than their older counterparts, it is not androgenic but part of the fur complex. The sensitivity to androgens seems to have been acquired by humans on the gene KRT37 relatively recently.
Vellus hair
Vellus hair grows individually or in small patches of varying, and sometimes irregular, length (2–4 cm). These irregularities are governed by genetics, and often persist throughout a lifetime. This kind of hair growth is usually not harmful.
Human hair color
Natural hair color can be brown, blond, black, red, or white; all natural hair colors including grey, white and lightest blond, are shades of brown.
Prostaglandin D2
A 2012 research paper indicates a causal link between elevated levels of localized PGD and hair growth inhibition. Applied topically, the researchers found PGD prevents hair growth, and mice that were genetically inclined to produce higher levels of PGD had inhibited hair growth. The researchers also found PGD levels were much higher in balding scalp tissue than nonbalding scalp tissue, through increased levels of prostaglandin D2 synthase. The paper suggested that inhibition of hair growth involved binding of PGD to a receptor called GPR44, and that GPR44 therefore would be a therapeutic target for androgenic alopecia in both men and women with hair loss and thinning. Because PGD's relation to asthma has been known for several years, several drugs that seek to reduce the effect of PGD through blocking the GPR44 are already in clinical trials.
Evolution of the brain
The evolutionary history of the human brain shows primarily a gradually bigger brain relative to body size during the evolutionary path from early primates to hominids and finally to "Homo sapiens". Human brain size has been trending upwards since 2 million years ago, with a 3 factor increase. Early australopithecine brains were a little larger than chimpanzee brains. The increase has been seen as larger human brain volume as we progressed along the human timeline of evolution (see Homininae), starting from about 600 cm in "Homo habilis" up to 1600 cm in "Homo neanderthalensis" (male averages). 
The increase in brain size topped with Neanderthals; 
Brain size of "Homo sapiens" varies significantly between population (races), with male averages ranging between about 1,200 to 1,450 cm.
Hair
Jablonski asserts head hair was evolutionarily advantageous for pre-humans to retain because it protected the scalp as they walked upright in the intense African (equatorial) UV light. While some might argue that, by this logic, humans should also express hairy shoulders because these body parts would putatively be exposed to similar conditions, the protection of the head, the seat of the brain that enabled humanity to become one of the most successful species on the planet (and which also is very vulnerable at birth) was arguably a more urgent issue (axillary hair in the underarms and groin were also retained as signs of sexual maturity). Sometime during the gradual process by which "Homo erectus" began a transition from furry skin to the naked skin expressed by Homo sapiens, hair texture putatively gradually changed from straight hair (the condition of most mammals, including humanity's closest cousins—chimpanzees) to Afro-textured hair or 'kinky' (i.e. tightly coiled). This argument assumes that curly hair better impedes the passage of UV light into the body relative to straight hair (thus curly or coiled hair would be particularly advantageous for light-skinned hominids living at the equator).
Hair loss
Hair follicle growth occurs in cycles. Each cycle consists of a long growing phase (anagen), a short transitional phase (catagen) and a short resting phase (telogen). At the end of the resting phase, the hair falls out (exogen) and a new hair starts growing in the follicle beginning the cycle again.
Ponytail
The numerical values used in this equation were the average density of human hair (1.3 grams per cubic centimeter), a bending modulus ( "A" ) of 8 × 10 Newton meter, a linear mass density of hair ( "λ" ) of 65 micrograms per centimeter and the major diameter of the hair (human hair is elliptical in cross section) of 79 ± 16 micrometers. "N" was taken to be 100,000 - the average numbers of hairs on a human head. The constant "E" was that of nylon which is similar to hair in its bend and twist moduli. The length "L" was taken to be 25 centimeters. These values give a length at which gravity bends a hair of "l" = 5.
Hair ice
Hair ice forms on moist, rotting wood from broadleaf trees when temperatures are slightly under and the air is humid. Each of the smooth, silky hairs has a diameter of about and a length of up to . The hairs are brittle, but take the shape of curls and waves. They can maintain their shape for hours and sometimes days. This long lifetime indicates that something is preventing the small ice crystals from recrystallizing into larger ones, since recrystallization normally occurs very quickly at temperatures near .
Facial hair
Facial hair is hair grown on the face, usually on the chin, cheeks, and upper lip region. It is typically a secondary sex characteristic of human males. Men typically start developing facial hair in the later years of puberty or adolescence, between seventeen and twenty years of age, and most do not finish developing a full adult beard until their early twenties or later. This varies, as boys may first develop facial hair between fourteen and sixteen years of age, and boys as young as eleven have been known to develop facial hair. Women are also capable of developing facial hair, especially after menopause, though typically significantly less than men. Men may style their facial hair into beards, moustaches, goatees or sideburns; others completely shave their facial hair. The term "whiskers", when used to refer to human facial hair, indicates the hair on the chin and cheeks.
Eyelash
The eyelashes of the human embryo develop from the ectoderm between the 22nd and 26th week of pregnancy. Natural eyelashes do not grow beyond a certain length, and fall off by themselves without any need for trimming. Eyelashes take about seven to eight weeks to grow back if pulled out, but constant pulling may lead to permanent damage. Their color may differ from that of the hair, although they tend to be dark on someone with dark hair and lighter on someone with light hair. Eyelash hair is not androgenic and is therefore not affected by puberty.
Body hair
Rising levels of androgen during puberty cause vellus hair to transform into terminal hair over many areas of the body. The sequence of appearance of terminal hair reflects the level of androgen sensitivity, with pubic hair being the first to appear due to the area's special sensitivity to androgen. The appearance of pubic hair in both sexes is usually seen as an indication of the start of a person's puberty. There is a sexual differentiation in the amount and distribution of androgenic hair, with men tending to have more terminal hair in more areas. This includes facial hair, chest hair, abdominal hair, leg hair, arm hair, and foot hair. Women retain more of the less visible vellus hair, although leg, arm, and foot hair can be noticeable on women. It is not unusual for women to have a few terminal hairs around their nipples as well.
In the later decades of life, especially after the 5th decade, there begins a noticeable reduction in body hair especially in the legs. The reason for this is not known but it could be due to poorer circulation, lower free circulating hormone amounts or other reasons.