Androgenic hair
Encyclopedia
Androgenic hair, colloquially body hair, is the terminal hair
that develops on the body
during and after puberty
. It is differentiated from the head hair
and less visible vellus hair, which are much finer and lighter in color. The growth of androgenic hair is related to the level of androgen
s (male hormone
s) in the individual. Due to a normally higher level of androgen, men tend to have more androgenic hair than women.
From childhood
onward, regardless of gender
, vellus hair covers almost the entire area of the human body. Exceptions include the lips, the backs of the ear
s, the palms of hand
s, the soles of the feet
, certain external genital areas, the navel
and scar
tissue. The density of hair – the number of hair follicle
s per area
of skin – varies from person to person. In many cases, areas on the human body that contain vellus hair will begin to produce darker, thicker body hair. An example of this is the growth of an adolescent's beard on a once smooth chin.
Androgenic hair follows the same growth pattern as the hair that grows on the scalp, only the anagen phase is shorter, and the telogen phase is longer. While the anagen phase for the hair on one's head lasts for years, the androgenic hair growing phase lasts a few months. The telogen phase for body hair lasts close to a year. This shortened growing period and extended dormant period explains why the hair on the head tends to be much longer than other hair found on the body. Differences in length seen in comparing the hair on the back of the hand and pubic hair, for example, can be explained by varied growth cycles in those two regions. The same goes for differences in body hair length seen in different people, especially when comparing men and women.
Hair follicles are to varying degrees sensitive to androgen, primarily testosterone
and its derivatives, 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.
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 especial 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
and 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.
. Terminal hair growth in adolescent and adult males is often much more intense than that in females, particularly for individuals with dark hair. In some cultures, it is common for women to remove arm hair, though this practice is less frequent than that of leg hair removal.
Terminal hair growth on arm
s 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 arm vellus hair growth sometimes occurs in young women and girls.
, including cultural practice or individual needs. Around the world, females generally shave their leg hair more regularly than men, to conform with the social norms of many cultures, many of which perceive smooth skin as a sign of youth and beauty. However, athletes of both sexes – swimmers
, runners
, cyclists and bodybuilders
in particular – may shave their androgenic hair to reduce friction, highlight muscular development or to make it easier to get into and out of skin-tight clothing. The main reason why professional cyclists shave their legs is to make treatment of road rash
less difficult.
is a collection of coarse hair found in the pubic region. It will often also grow on the thighs and abdomen. Zoologist Desmond Morris
disputes theories that it developed to signal sexual maturity or protect the skin from chafing during copulation, and prefers the explanation that pubic hair acts as a scent trap.
The genital area of males and females are first inhabited by shorter, lighter vellus hairs that are next to invisible and only begin to develop into darker, thicker pubic hair at puberty
. At this time, the pituitary gland
secretes gonadotropin
hormones which trigger the production of testosterone in the ovaries, respectively testicles promoting pubic hair growth. The average ages pubic hair begins to grow in males and females are 12 and 11, respectively.
Just as individual people differ in scalp hair color, they can also differ in pubic hair color. Differences in thickness, growth rate, and length are also evident.
, as the name suggests, grows primarily on or around one's face
. Both men and women experience facial hair growth, even though it is commonly accepted as a masculine
trait. Like pubic hair, non-vellus facial hair will begin to grow in around puberty. Moustache
s in young men usually begin to grow in at around the age of 13, although some men may not grow a moustache until they reach late teens.
and the thermal properties of hair itself.
The thermodynamic properties of hair are based on the properties of the keratin
strands and amino acids that combine into a 'coiled' structure. This structure lends to many of the properties of hair, such as its ability to stretch and return to its original length. It should be noted that this coiled structure does not predispose curly or frizzy hair, both of which are defined by oval or triangular hair follicle cross-sections.
Markus J. Rantala of the Department of Biological and Environmental Science, University of Jyväskylä
, Finland
, said humans evolved by "natural selection" to be hairless when the trade off of having "having fewer parasites" became more important than having a "warming, furry coat".
P.E. Wheeler of the Department of Biology at Liverpool Polytechnic said quadrupedal Savannah
mammal
s 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.
Markus J. Rantala of the Department of Biological and Environmental Science, University of Jyväskylä
, Finland
, said the existence of "androgen dependent" hair on men "could be" explained by "sexual attraction" whereby hair on the genitals would trap "pheromones" and hair on the chin would make the chin appear "more massive".
According to Ashley Montagu
who taught anthropology at Princeton University, the "Mongoloid
, "Bushmen
" and "Negroid
" are less hairy than the "Caucasoid" and Montagu said that the hairless feature is a neotenous
trait.
Rodney P.R. Dawber of the Oxford Hair Foundation and Clinical Lecturer in Dermatology said "Mongoloid males" have "little or no facial or body hair" and Dawber also said "Mediterranean
males are covered with an exuberant pelage".
Anthropologist Arnold Henry Savage Landor
described the Ainu
as having hairy bodies.
C.H. Danforth and Mildred Trotter
of the Department of Anatomy at Washington University did a study using army soldiers of European origin where they concluded that dark-haired white
men are generally more hairy than fair-haired white men.
H. Harris who published in the British Journal of Dermatology said American Indian
s have the least body hair, Chinese
and "Negroes" have little body hair, white people
have more body hair than "Negroes" and Ainu
have the most body hair.
Milkica Nešić et al. of the Department of Physiology at the University of Niš
, Serbia
, said the "frequency of hair" in "peoples of the Caucasus
" is "significantly higher than" in "Negroid
populations".
Eike-Meinrad Winkler and Kerrin Christiansen of the Institut für Humanbiologie, Hamburg
, Germany
, did a study using Kavango people and !Kung
people of body hair and hormone levels to investigate the reason Black Africans did not have bodies as hairy as Europeans. Winkler and Christiansen concluded the difference in hairiness between Black Africans and Europeans had to do with differences in androgen
or estradiol
production, in androgen metabolism
, and in sex hormone action in the target cells.
Valerie Anne Randall of the Department of Biomedical Sciences, University of Bradford
, said beard growth in Caucasian men increases until the mid-thirties due to a delay caused by growth cycles changing from vellus hair to terminal hair
. Randall said Caucasian men and women are hairier than Japanese men and women even with the same "total plasma androgen
levels". Randall says that the reason for some people being hairy and some people not being hairy is unclear, but that it probably is related to differing sensitivity of hair follicle
s to 5α-reductase.
Stewart W. Hindley and Albert Damon of the Department of Anthropology at Stanford University
said "Caucasians" are hairier than "Negroids
" and "Mongoloids
". Hindley and Damon said different groups of people have differing percentages of members with mid-phalangeal hair: Andamanese
0%, Eskimo
1%, American "Negroes" 16% or 28%, Ethiopians
25.6%, Mexicans
of the Yucatan
20.9%, Penobscot and Shinnecook 22.7%, Gurkha
33.6%, Japanese
44.6%, "various Hindu
s" 40-50%, Egyptians 52.3%, Near Eastern peoples 62-71% , "various Europeans" 60-80%.
Anthropologist Joseph Deniker
said the "very hairy" peoples are the Ainu
s, Iranians, Australian aborigines, Toda
, Dravidians and Melanesians while Deniker said the American Indian
, Bushmen
, West African
, Mongol
and Malay
people are "glabrous" (not hairy). Deniker said hairy peoples have thicker beards, eyelashes and eyebrows, but Deniker said hairy people tend to have fewer hairs on their scalp.
Terminal hair
Terminal hairs are thick, long, and dark, as compared with vellus hair. During puberty, the increase in androgenic hormone levels causes vellus hair to be replaced with terminal hair in certain parts of the human body...
that develops on the body
Body
With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...
during and after puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
. It is differentiated from the head hair
Hair
Hair is a filamentous biomaterial, that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class....
and less visible vellus hair, which are much finer and lighter in color. The growth of androgenic hair is related to the level of androgen
Androgen
Androgen, also called androgenic hormone or testoid, is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors...
s (male hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s) in the individual. Due to a normally higher level of androgen, men tend to have more androgenic hair than women.
From childhood
Childhood
Childhood is the age span ranging from birth to adolescence. In developmental psychology, childhood is divided up into the developmental stages of toddlerhood , early childhood , middle childhood , and adolescence .- Age ranges of childhood :The term childhood is non-specific and can imply a...
onward, regardless of gender
Gender
Gender is a range of characteristics used to distinguish between males and females, particularly in the cases of men and women and the masculine and feminine attributes assigned to them. Depending on the context, the discriminating characteristics vary from sex to social role to gender identity...
, vellus hair covers almost the entire area of the human body. Exceptions include the lips, the backs of the ear
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
s, the palms of hand
Hand
A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
s, the soles of the feet
Foot
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws...
, certain external genital areas, the navel
Navel
The navel is a scar on the abdomen caused when the umbilical cord is removed from a newborn baby...
and scar
Scar
Scars are areas of fibrous tissue that replace normal skin after injury. A scar results from the biological process of wound repair in the skin and other tissues of the body. Thus, scarring is a natural part of the healing process. With the exception of very minor lesions, every wound results in...
tissue. The density of hair – the number of hair follicle
Hair follicle
A hair follicle is a skin organ that produces hair. Hair production occurs in phases, including a growth phase , and cessation phase , and a rest phase . Stem cells are principally responsible for the production of hair....
s per area
Area
Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...
of skin – varies from person to person. In many cases, areas on the human body that contain vellus hair will begin to produce darker, thicker body hair. An example of this is the growth of an adolescent's beard on a once smooth chin.
Androgenic hair follows the same growth pattern as the hair that grows on the scalp, only the anagen phase is shorter, and the telogen phase is longer. While the anagen phase for the hair on one's head lasts for years, the androgenic hair growing phase lasts a few months. The telogen phase for body hair lasts close to a year. This shortened growing period and extended dormant period explains why the hair on the head tends to be much longer than other hair found on the body. Differences in length seen in comparing the hair on the back of the hand and pubic hair, for example, can be explained by varied growth cycles in those two regions. The same goes for differences in body hair length seen in different people, especially when comparing men and women.
Development and growth
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...
and its derivatives, 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.
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
Pubic hair
Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region....
being the first to appear due to the area's especial 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
Sexual differentiation
Sexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote...
in the amount and distribution of androgenic hair, with men tending to have more terminal hair in more areas. This includes facial hair
Facial hair
Facial hair is a secondary sex characteristic of human males. Men often start developing facial hair in the later years of puberty or adolescence, approximately between 17–20 years of age, and most do not finish developing a fully adult beard until their early 20s or even later...
, chest hair
Chest hair
The term chest hair is generally used to describe hair that grows on the chest of human males, in the region between the neck and the abdomen. Chest hair, which is a secondary sex characteristic, develops during and after puberty...
, abdominal hair
Abdominal hair
The term abdominal hair refers to the hair that grows on the abdomen of humans and non-human mammals, in the region between the pubic area and the thorax . The growth of abdominal hair follows the same pattern on nearly all mammals, vertically from the pubic area upwards and from the thorax...
, leg
Leg hair
Leg hair is hair that grows on the legs of humans, generally appearing at the onset of adulthood.Male legs are most often hairier than female ones. The amount of hair on an individuals legs can depend on their ethnic background...
and 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.
Growth distribution
Like much of the hair on the human body, leg, arm, chest, and back hair begin as vellus hair. As people age, the hair in these regions will often begin to grow darker and more abundantly. This will typically happen during or after puberty. Men will generally have more abundant, coarser hair on the legs, arms, chest, and back, while women tend to have a less drastic change in the hair growth in these areas. However, some women will grow darker, longer hair in one or more of these regions.Arms
Arm hair grows on a human's forearms, sometimes even on the elbow area. Terminal arm hair is concentrated on the wrist end of the forearm, extending over the handHand
A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
. Terminal hair growth in adolescent and adult males is often much more intense than that in females, particularly for individuals with dark hair. In some cultures, it is common for women to remove arm hair, though this practice is less frequent than that of leg hair removal.
Terminal hair growth on arm
Arm
In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods...
s 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 arm vellus hair growth sometimes occurs in young women and girls.
Feet
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.Legs
Leg hair generally appears at the onset of adulthood, with the legs of men most often hairier than those of women. For a variety of reasons, people may shave their leg hairLeg shaving
Leg shaving is the practice of removing leg hair by shaving the hair off using a razor or electric shaver. In addition, some people remove leg hair using waxing, sugaring, depilatories, depilation devices, or lasers, but shaving remains the least expensive method.It is a very common practice among...
, including cultural practice or individual needs. Around the world, females generally shave their leg hair more regularly than men, to conform with the social norms of many cultures, many of which perceive smooth skin as a sign of youth and beauty. However, athletes of both sexes – swimmers
Swimming (sport)
Swimming is a sport governed by the Fédération Internationale de Natation .-History: Competitive swimming in Europe began around 1800 BCE, mostly in the form of the freestyle. In 1873 Steve Bowyer introduced the trudgen to Western swimming competitions, after copying the front crawl used by Native...
, runners
Track and field
Track and field is a sport comprising various competitive athletic contests based around the activities of running, jumping and throwing. The name of the sport derives from the venue for the competitions: a stadium which features an oval running track surrounding a grassy area...
, cyclists and bodybuilders
Bodybuilding
Bodybuilding is a form of body modification involving intensive muscle hypertrophy. An individual who engages in this activity is referred to as a bodybuilder. In competitive and professional bodybuilding, bodybuilders display their physiques to a panel of judges, who assign points based on their...
in particular – may shave their androgenic hair to reduce friction, highlight muscular development or to make it easier to get into and out of skin-tight clothing. The main reason why professional cyclists shave their legs is to make treatment of road rash
Road rash
Road rash is a colloquial term for skin and bone injury caused by abrasion with road surfaces, usually as a consequence of cycling and motorcycling accidents. The term may be applied to both a fresh injury and the scar tissue left by an old one...
less difficult.
Pubic
Pubic hairPubic hair
Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region....
is a collection of coarse hair found in the pubic region. It will often also grow on the thighs and abdomen. Zoologist Desmond Morris
Desmond Morris
Desmond John Morris, born 24 January 1928 in Purton, north Wiltshire, is a British zoologist and ethologist, as well as a popular anthropologist. He is also known as a painter, television presenter and popular author.-Life:...
disputes theories that it developed to signal sexual maturity or protect the skin from chafing during copulation, and prefers the explanation that pubic hair acts as a scent trap.
The genital area of males and females are first inhabited by shorter, lighter vellus hairs that are next to invisible and only begin to develop into darker, thicker pubic hair at puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
. At this time, the pituitary gland
Pituitary gland
In vertebrate anatomy the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 g , in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity covered by a dural fold...
secretes gonadotropin
Gonadotropin
Gonadotropins are protein hormones secreted by gonadotrope cells of the pituitary gland of vertebrates. This is a family of proteins, which include the mammalian hormones follitropin , lutropin , placental chorionic gonadotropins hCG and eCG and chorionic gonadotropin , as well as at least two...
hormones which trigger the production of testosterone in the ovaries, respectively testicles promoting pubic hair growth. The average ages pubic hair begins to grow in males and females are 12 and 11, respectively.
Just as individual people differ in scalp hair color, they can also differ in pubic hair color. Differences in thickness, growth rate, and length are also evident.
Facial
Facial hairFacial hair
Facial hair is a secondary sex characteristic of human males. Men often start developing facial hair in the later years of puberty or adolescence, approximately between 17–20 years of age, and most do not finish developing a fully adult beard until their early 20s or even later...
, as the name suggests, grows primarily on or around one's face
Face
The face is a central sense organ complex, for those animals that have one, normally on the ventral surface of the head, and can, depending on the definition in the human case, include the hair, forehead, eyebrow, eyelashes, eyes, nose, ears, cheeks, mouth, lips, philtrum, temple, teeth, skin, and...
. Both men and women experience facial hair growth, even though it is commonly accepted as a masculine
Masculine
Masculine or masculinity, normally refer to qualities positively associated with men.Masculine may also refer to:*Masculine , a grammatical gender*Masculine cadence, a final chord occurring on a strong beat in music...
trait. Like pubic hair, non-vellus facial hair will begin to grow in around puberty. Moustache
Moustache
A moustache is facial hair grown on the outer surface of the upper lip. It may or may not be accompanied by a type of beard, a facial hair style grown and cropped to cover most of the lower half of the face.-Etymology:...
s in young men usually begin to grow in at around the age of 13, although some men may not grow a moustache until they reach late teens.
Function
Androgenic hair provides tactile sensory input by transferring hair movement and vibration via the shaft to sensory nerves within the skin. Follicular nerves detect displacement of hair shafts and other nerve ending in the surrounding skin detect vibration and distortions of the skin around the follicles. Androgenic hair extends the sense of touch beyond the surface of the skin into the air and space surrounding it, detecting air movements as well as hair displacement from contact by insects or objects.Evolution
Determining the evolutionary function of androgenic hair must take into account both human evolutionHuman evolution
Human evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...
and the thermal properties of hair itself.
The thermodynamic properties of hair are based on the properties of the keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
strands and amino acids that combine into a 'coiled' structure. This structure lends to many of the properties of hair, such as its ability to stretch and return to its original length. It should be noted that this coiled structure does not predispose curly or frizzy hair, both of which are defined by oval or triangular hair follicle cross-sections.
Evolution of less body hair
Hair is a very good thermal conductor and aids both heat transfer into and out of the body. This is often seen as a problem with straighteners and blow drying as the hair quickly transfers the heat into the inner hair shaft and heats the water in the hair to boiling point resulting in dry brittle hair if silicone insulating oils are not used. When goose pimples are observed, small muscles contract to raise the hairs both to provide insulation, by reducing cooling by air convection of the skin, as well as in response to central nervous stimulus, similar to the feeling of 'hairs standing up on the back of your neck'. This phenomenon also occurs when static charge is built up and stored in the hair. Keratin however can easily be damaged by excessive heat and dryness, suggesting that extreme sun exposure, perhaps due to a lack of clothing, would result in perpetual hair destruction, eventually resulting in the genes being bred out in favor of high skin pigmentation. It is also true that parasites can live on and in hair thus peoples who preserved their body hair would have required greater general hygiene in order to prevent diseases caused by such as well as a need for grooming, two predominant factors in the civilization of homo sapiens.Markus J. Rantala of the Department of Biological and Environmental Science, University of Jyväskylä
University of Jyväskylä
The University of Jyväskylä is a university in Jyväskylä, Finland. It has its origins in the first Finnish-speaking teacher training college , founded in 1863. Around 14,000 students are currently enrolled in the degree programs of the university...
, Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
, said humans evolved by "natural selection" to be hairless when the trade off of having "having fewer parasites" became more important than having a "warming, furry coat".
P.E. Wheeler of the Department of Biology at Liverpool Polytechnic said quadrupedal Savannah
Savannah
Savannah or savanna is a type of grassland.It can also mean:-People:* Savannah King, a Canadian freestyle swimmer* Savannah Outen, a singer who gained popularity on You Tube...
mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s 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.
Sexual selection
Cambridge University zoologist Charles Goodhart believed men have long preferred the "hairless trait" in women, ever since the existence of the "hairless trait" occurred in our hairy forebears 70,000-120,000 years ago during the last episode of global warming. Goodhart argued that humans are relatively hairless today compared to our ancestors because women who were sexually selected for their "hairless trait" passed it on to both their male and female offspring.Markus J. Rantala of the Department of Biological and Environmental Science, University of Jyväskylä
University of Jyväskylä
The University of Jyväskylä is a university in Jyväskylä, Finland. It has its origins in the first Finnish-speaking teacher training college , founded in 1863. Around 14,000 students are currently enrolled in the degree programs of the university...
, Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
, said the existence of "androgen dependent" hair on men "could be" explained by "sexual attraction" whereby hair on the genitals would trap "pheromones" and hair on the chin would make the chin appear "more massive".
Across races
| Frequency and Appearance of Terminal Hair in 239 Adult White Males by Stanley Marion Garn Stanley Marion Garn Stanley Marion Garn Ph.D. was a professor of physical anthropology. He was a professor of anthropology at the College for Literature, Science and Arts and a Professor of Nutrition at the School of Public Health at the University of Michigan... of Harvard University Harvard University Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country... |
|||
|---|---|---|---|
| Region | Percent | Region | Percent |
| beard Beard A beard is the collection of hair that grows on the chin, cheeks and neck of human beings. Usually, only pubescent or adult males are able to grow beards. However, women with hirsutism may develop a beard... |
100% | abdominal Abdomen In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity... |
84% |
| thoracic Thorax The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:... |
79% | lower arm & leg | 97% |
| upper arm & leg | 85% | |gluteal Gluteal muscles The gluteal muscles are the three muscles that make up the buttocks: the gluteus maximus muscle, gluteus medius muscle and gluteus minimus muscle.-The gluteal muscles:... |
37% |
| sacral Sacrum In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx... |
43% | lower back | 28% |
| upper back Back - People :* Adam Back, British cryptographer* Charles Back, South African winemaker* Chris Back , Australian politician* Ernst Emil Alexander Back , German physicist* Frédéric Back , Canadian animator... |
25% | mid-phalageal | 67% |
According to Ashley Montagu
Ashley Montagu
Montague Francis Ashley Montagu was a British-American anthropologist and humanist, of Jewish ancestry, who popularized topics such as race and gender and their relation to politics and development...
who taught anthropology at Princeton University, the "Mongoloid
Mongoloid race
Mongoloid is a term sometimes used by forensic anthropologists and physical anthropologists to refer to populations that share certain phenotypic traits such as epicanthic fold and shovel-shaped incisors and other physical traits common in East Asia, the Americas and the Arctic...
, "Bushmen
Bushmen
The indigenous people of Southern Africa, whose territory spans most areas of South Africa, Zimbabwe, Lesotho, Mozambique, Swaziland, Botswana, Namibia, and Angola, are variously referred to as Bushmen, San, Sho, Barwa, Kung, or Khwe...
" and "Negroid
Negroid race
Negroid is a term sometimes used by forensic anthropologists and physical anthropologists to refer to populations that share certain phenotypic traits such as high Melanin levels and skeletal features associated with ancestry from Sub-saharan Africa.It was introduced by early Racial science used...
" are less hairy than the "Caucasoid" and Montagu said that the hairless feature is a neotenous
Neoteny
Neoteny , also called juvenilization , is one of the two ways by which paedomorphism can arise. Paedomorphism is the retention by adults of traits previously seen only in juveniles, and is a subject studied in the field of developmental biology. In neoteny, the physiological development of an...
trait.
Rodney P.R. Dawber of the Oxford Hair Foundation and Clinical Lecturer in Dermatology said "Mongoloid males" have "little or no facial or body hair" and Dawber also said "Mediterranean
Mediterranean race
The Mediterranean race was one of the three sub-categories into which the Caucasian race and the people of Europe were divided by anthropologists in the late nineteenth and early twentieth centuries, following the publication of William Z. Ripley's book The Races of Europe...
males are covered with an exuberant pelage".
Anthropologist Arnold Henry Savage Landor
Arnold Henry Savage Landor
Arnold Henry Savage Landor was an English painter, explorer, writer and anthropologist, born in Florence. His grandfather was the poet and writer Walter Savage Landor, who himself lived for long periods in Florence....
described the Ainu
Ainu people
The , also called Aynu, Aino , and in historical texts Ezo , are indigenous people or groups in Japan and Russia. Historically they spoke the Ainu language and related varieties and lived in Hokkaidō, the Kuril Islands, and much of Sakhalin...
as having hairy bodies.
C.H. Danforth and Mildred Trotter
Mildred Trotter
Mildred Trotter was an important 20th century forensic anthropologist.Trotter was born in Monaca, Pennsylvania. She received her B.A. in zoology and physiology from Mount Holyoke College in 1920 and her Ph.D. from Washington University in St. Louis in 1924...
of the Department of Anatomy at Washington University did a study using army soldiers of European origin where they concluded that dark-haired white
White people
White people is a term which usually refers to human beings characterized, at least in part, by the light pigmentation of their skin...
men are generally more hairy than fair-haired white men.
H. Harris who published in the British Journal of Dermatology said American Indian
American Indian
American Indian may refer to:*Native Americans in the United States*Indigenous people of the Americas, the inhabitants of North and South America prior to the arrival of Christopher Columbus*Indian American, an American with ancestors from India...
s have the least body hair, Chinese
Chinese people
The term Chinese people may refer to any of the following:*People with Han Chinese ethnicity ....
and "Negroes" have little body hair, white people
White people
White people is a term which usually refers to human beings characterized, at least in part, by the light pigmentation of their skin...
have more body hair than "Negroes" and Ainu
Ainu
Ainu or Aynu may refer to:*Ainu people, of Japan and the Russian Far East**Ainu language**Ainu music**Ainu cuisine*Ainu , a primordial spirit in J. R. R. Tolkien's fantasy writings*Äynu people, of Western China...
have the most body hair.
Milkica Nešić et al. of the Department of Physiology at the University of Niš
University of Niš
The University of Niš is a university located in Niš, Serbia. It was founded in 1965 and it consists of 13 faculties with 1500 teachers, 630 staff and extracurricular staff, and around 30,000 students...
, Serbia
Serbia
Serbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...
, said the "frequency of hair" in "peoples of the Caucasus
Caucasian peoples
This article deals with the various ethnic groups inhabiting the Caucasus region. There are more than50 ethnic groups living in the region.-Peoples speaking Caucasian languages:...
" is "significantly higher than" in "Negroid
Negroid race
Negroid is a term sometimes used by forensic anthropologists and physical anthropologists to refer to populations that share certain phenotypic traits such as high Melanin levels and skeletal features associated with ancestry from Sub-saharan Africa.It was introduced by early Racial science used...
populations".
Eike-Meinrad Winkler and Kerrin Christiansen of the Institut für Humanbiologie, Hamburg
Hamburg
-History:The first historic name for the city was, according to Claudius Ptolemy's reports, Treva.But the city takes its modern name, Hamburg, from the first permanent building on the site, a castle whose construction was ordered by the Emperor Charlemagne in AD 808...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, did a study using Kavango people and !Kung
!Kung
ǃKung, also spelled !Xun, may refer to:* ǃKung people* ǃKung languageSee also ǃXu ....
people of body hair and hormone levels to investigate the reason Black Africans did not have bodies as hairy as Europeans. Winkler and Christiansen concluded the difference in hairiness between Black Africans and Europeans had to do with differences in androgen
Androgen
Androgen, also called androgenic hormone or testoid, is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors...
or estradiol
Estradiol
Estradiol is a sex hormone. Estradiol is abbreviated E2 as it has 2 hydroxyl groups in its molecular structure. Estrone has 1 and estriol has 3 . Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect...
production, in androgen metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
, and in sex hormone action in the target cells.
Valerie Anne Randall of the Department of Biomedical Sciences, University of Bradford
University of Bradford
The University of Bradford is a British university located in the city of Bradford, West Yorkshire, England. The University received its Royal Charter in 1966, making it the 40th University to be created in Britain, but its origins date back to the early 1800s...
, said beard growth in Caucasian men increases until the mid-thirties due to a delay caused by growth cycles changing from vellus hair to terminal hair
Terminal hair
Terminal hairs are thick, long, and dark, as compared with vellus hair. During puberty, the increase in androgenic hormone levels causes vellus hair to be replaced with terminal hair in certain parts of the human body...
. Randall said Caucasian men and women are hairier than Japanese men and women even with the same "total plasma androgen
Androgen
Androgen, also called androgenic hormone or testoid, is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors...
levels". Randall says that the reason for some people being hairy and some people not being hairy is unclear, but that it probably is related to differing sensitivity of hair follicle
Hair follicle
A hair follicle is a skin organ that produces hair. Hair production occurs in phases, including a growth phase , and cessation phase , and a rest phase . Stem cells are principally responsible for the production of hair....
s to 5α-reductase.
Stewart W. Hindley and Albert Damon of the Department of Anthropology at Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
said "Caucasians" are hairier than "Negroids
Negroid race
Negroid is a term sometimes used by forensic anthropologists and physical anthropologists to refer to populations that share certain phenotypic traits such as high Melanin levels and skeletal features associated with ancestry from Sub-saharan Africa.It was introduced by early Racial science used...
" and "Mongoloids
Mongoloid race
Mongoloid is a term sometimes used by forensic anthropologists and physical anthropologists to refer to populations that share certain phenotypic traits such as epicanthic fold and shovel-shaped incisors and other physical traits common in East Asia, the Americas and the Arctic...
". Hindley and Damon said different groups of people have differing percentages of members with mid-phalangeal hair: Andamanese
Andamanese
The Andamanese people are the various aboriginal inhabitants of the Andaman Islands, which is the northern district of the Andaman and Nicobar Islands union territory of India, located in the southeastern part of the Bay of Bengal. They include the Great Andamanese, Jarawa, Onge, Sentinelese, and...
0%, Eskimo
Eskimo
Eskimos or Inuit–Yupik peoples are indigenous peoples who have traditionally inhabited the circumpolar region from eastern Siberia , across Alaska , Canada, and Greenland....
1%, American "Negroes" 16% or 28%, Ethiopians
Ethiopian people
Ethiopian people or Ethnic Ethiopians are an ethnic group found in the horn of African country of Ethiopia.-Origins:Ethnic Ethiopians are one of the nearly 80 ethnic groups of the horn of Africa country and are found in every regional state of Ethiopia...
25.6%, Mexicans
Mexican people
Mexican people refers to all persons from Mexico, a multiethnic country in North America, and/or who identify with the Mexican cultural and/or national identity....
of the Yucatan
Yucatán
Yucatán officially Estado Libre y Soberano de Yucatán is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 106 municipalities and its capital city is Mérida....
20.9%, Penobscot and Shinnecook 22.7%, Gurkha
Gurkha
Gurkha are people from Nepal who take their name from the Gorkha District. Gurkhas are best known for their history in the Indian Army's Gorkha regiments, the British Army's Brigade of Gurkhas and the Nepalese Army. Gurkha units are closely associated with the kukri, a forward-curving Nepalese knife...
33.6%, Japanese
Japanese people
The are an ethnic group originating in the Japanese archipelago and are the predominant ethnic group of Japan. Worldwide, approximately 130 million people are of Japanese descent; of these, approximately 127 million are residents of Japan. People of Japanese ancestry who live in other countries...
44.6%, "various Hindu
Hindu
Hindu refers to an identity associated with the philosophical, religious and cultural systems that are indigenous to the Indian subcontinent. As used in the Constitution of India, the word "Hindu" is also attributed to all persons professing any Indian religion...
s" 40-50%, Egyptians 52.3%, Near Eastern peoples 62-71% , "various Europeans" 60-80%.
Anthropologist Joseph Deniker
Joseph Deniker
Joseph Deniker was a French naturalist and anthropologist, known primarily for his attempts to develop highly-detailed maps of race in Europe.- Life :...
said the "very hairy" peoples are the Ainu
Ainu
Ainu or Aynu may refer to:*Ainu people, of Japan and the Russian Far East**Ainu language**Ainu music**Ainu cuisine*Ainu , a primordial spirit in J. R. R. Tolkien's fantasy writings*Äynu people, of Western China...
s, Iranians, Australian aborigines, Toda
Toda people
The Toda people are a small pastoral community who live on the isolated Nilgiri plateau of Southern India. Before the late 18th century, the Toda coexisted locally with other communities, including the Badaga, Kota, and Kuruba, in a loose caste-like community organization in which the Toda were...
, Dravidians and Melanesians while Deniker said the American Indian
American Indian
American Indian may refer to:*Native Americans in the United States*Indigenous people of the Americas, the inhabitants of North and South America prior to the arrival of Christopher Columbus*Indian American, an American with ancestors from India...
, Bushmen
Bushmen
The indigenous people of Southern Africa, whose territory spans most areas of South Africa, Zimbabwe, Lesotho, Mozambique, Swaziland, Botswana, Namibia, and Angola, are variously referred to as Bushmen, San, Sho, Barwa, Kung, or Khwe...
, West African
Black people
The term black people is used in systems of racial classification for humans of a dark skinned phenotype, relative to other racial groups.Different societies apply different criteria regarding who is classified as "black", and often social variables such as class, socio-economic status also plays a...
, Mongol
Mongoloid race
Mongoloid is a term sometimes used by forensic anthropologists and physical anthropologists to refer to populations that share certain phenotypic traits such as epicanthic fold and shovel-shaped incisors and other physical traits common in East Asia, the Americas and the Arctic...
and Malay
Malay people
Malays are an ethnic group of Austronesian people predominantly inhabiting the Malay Peninsula, including the southernmost parts of Thailand, the east coast of Sumatra, the coast of Borneo, and the smaller islands which lie between these locations...
people are "glabrous" (not hairy). Deniker said hairy peoples have thicker beards, eyelashes and eyebrows, but Deniker said hairy people tend to have fewer hairs on their scalp.
See also
- AlopeciaAlopeciaAlopecia means loss of hair from the head or body. Alopecia can mean baldness, a term generally reserved for pattern alopecia or androgenic alopecia. Compulsive pulling of hair can also produce hair loss. Hairstyling routines such as tight ponytails or braids may induce Traction alopecia. Both...
- Hair removalHair removalHair removal is the removal of body hair, and describes the methods used to achieve that result.Hair typically grows all over the human body during and after puberty. Men tend to have more body hair than women. Both men and women tend to have hair on the head, eyebrows, eyelashes, armpits, pubic...
- HirsutismHirsutismHirsutism or frazonism is the excessive hairiness on women in those parts of the body where terminal hair does not normally occur or is minimal - for example, a beard or chest hair. It refers to a male pattern of body hair and it is therefore primarily of cosmetic and psychological concern...
- Human hair color
- TrichotillomaniaTrichotillomaniaTrichotillomania, which is classified as an impulse control disorder by DSM-IV, is the compulsive urge to pull out one's own hair leading to noticeable hair loss, distress, and social or functional impairment. It is often chronic and difficult to treat....