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Hair is a
protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms ...

protein filament
that grows from
follicles
follicles
found in the
dermis The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from s ...
. Hair is one of the defining characteristics of
mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
s. The
human body The human body is the structure of a Human, human being. It is composed of many different types of Cell (biology), cells that together create Tissue (biology), tissues and subsequently organ systems. They ensure homeostasis and the life, viabi ...

human body
, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fine
vellus hair Vellus hair is short, thin, light-colored, and barely noticeable hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of g ...
. Most common interest in hair is focused on
hair growth The growth of human hair occurs everywhere on the body except for the soles of the feet, the inside of the mouth, the lips, the backs of the ears, the palms of the hands, some external genital A sex organ (or reproductive organ) is any part of a ...
, hair types, and
hair care Hair care is an overall term for hygiene Hygiene is a series of practices performed to preserve health Health, according to the World Health Organization, is "a state of complete physical, Mental health, mental and social well-being and n ...
, but hair is also an important
biomaterial A biomaterial is a substance that has been engineered to interact with biological systems for a medical purpose, either a therapeutic (treat, augment, repair, or replace a tissue function of the body) or a diagnostic one. As a science, biomateria ...
primarily composed of
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
, notably
alpha-keratin Alpha-keratin, or α-keratin, is a type of keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin Alpha-keratin, or α-keratin, is a type of keratin Keratin () is one of a famil ...
. Attitudes towards different forms of hair, such as
hairstyle A hairstyle, hairdo, haircut or coiffure refers to the fashion, styling of hair, usually on the human scalp. Sometimes, this could also mean an editing of facial or body hair. The fashioning of hair can be considered an aspect of personal ...

hairstyle
s and
hair removal Hair removal, also known as epilation or depilation, is the deliberate removal of body hair or head hair. Hair typically grows all over the human body and can vary in thickness and length across human populations. Hair can become more visible d ...
, vary widely across different cultures and historical periods, but it is often used to indicate a person's personal beliefs or social position, such as their age, sex, or
religion Religion is a social Social organisms, including humans, live collectively in interacting populations. This interaction is considered social whether they are aware of it or not, and whether the exchange is voluntary/involuntary. Etymology ...

religion
.


Overview

The word "hair" usually refers to two distinct structures: #the part beneath the skin, called the
hair follicle The hair follicle is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given org ...

hair follicle
, or, when pulled from the skin, the bulb or root. This organ is located in the
dermis The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from s ...
and maintains
stem cell In multicellular organisms Multicellular organisms are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties ...
s, which not only re-grow the hair after it falls out, but also are recruited to regrow skin after a
wound A wound is a type of injury Injury, also known as physical trauma, is damage Damage is any change in a thing, often a physical object, that degrades it away from its initial state. It can broadly be defined as "changes introduced into a ...

wound
. # the hair shaft, which is the hard filamentous part that extends above the skin surface. A cross section of the hair shaft may be divided roughly into three zones. Hair fibers have a structure consisting of several layers, starting from the outside: # the
cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
, which consists of several layers of flat, thin cells laid out overlapping one another as roof shingles # the
cortex Cortex or cortical may refer to: Science Anatomy * Cortex (anatomy), the outermost or superficial layer of an organ * Cortex (hair), the middle layer of a strand of hair * Adrenal cortex, the portion of the adrenal gland that produces cortisol and ...
, which contains the
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin Alpha-keratin, or α-keratin, is a type of keratin Keratin () is one of a family of fibrous structural proteins known as Scleroprot ...

keratin
bundles in cell structures that remain roughly rod-like # the
medulla Medulla or Medullary may refer to: Science * Medulla oblongata, a part of the brain stem * Renal medulla, a part of the kidney * Adrenal medulla, a part of the adrenal gland * Medulla of ovary, a stroma in the center of the ovary * Medulla of th ...
, a disorganized and open area at the fiber's center


Description

Each strand of hair is made up of the
medulla Medulla or Medullary may refer to: Science * Medulla oblongata, a part of the brain stem * Renal medulla, a part of the kidney * Adrenal medulla, a part of the adrenal gland * Medulla of ovary, a stroma in the center of the ovary * Medulla of th ...
,
cortex Cortex or cortical may refer to: Science Anatomy * Cortex (anatomy), the outermost or superficial layer of an organ * Cortex (hair), the middle layer of a strand of hair * Adrenal cortex, the portion of the adrenal gland that produces cortisol and ...
, and
cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
.Hair Structure and Hair Life Cycle
follicle.com
The innermost region, the
medulla Medulla or Medullary may refer to: Science * Medulla oblongata, a part of the brain stem * Renal medulla, a part of the kidney * Adrenal medulla, a part of the adrenal gland * Medulla of ovary, a stroma in the center of the ovary * Medulla of th ...
, is not always present which is an open, unstructured region. The highly structural and organized
cortex Cortex or cortical may refer to: Science Anatomy * Cortex (anatomy), the outermost or superficial layer of an organ * Cortex (hair), the middle layer of a strand of hair * Adrenal cortex, the portion of the adrenal gland that produces cortisol and ...
, or second of three layers of the hair, is the primary source of mechanical strength and water uptake. The cortex contains
melanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigments found in most organisms. Melanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the ami ...

melanin
, which colors the
fiber Fiber or fibre (from la, fibra, links=no) is a natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including ...

fiber
based on the number, distribution and types of
melanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigments found in most organisms. Melanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the ami ...

melanin
granules. The shape of the follicle determines the shape of the cortex, and the shape of the
fiber Fiber or fibre (from la, fibra, links=no) is a natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including ...

fiber
is related to how straight or curly the hair is. People with straight hair have round hair fibers. Oval and other shaped fibers are generally more wavy or curly. The cuticle is the outer covering. Its complex structure slides as the hair swells and is covered with a single molecular layer of
lipid In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...
that makes the hair repel water. The diameter of human hair varies from . There are two million small, tubular glands and
sweat gland Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of an ...
s that produce watery fluids that cool the body by evaporation. The glands at the opening of the hair produce a fatty secretion that lubricates the hair. Hair growth begins inside the
hair follicle The hair follicle is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given org ...

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 A sebaceous gland is a microscopic exocrine Exocrine glands are gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek participle , "setting in motion") is a ...
which lubricates the hair and the
arrector pili The arrector pili muscles, also knows as hair erector muscles, are small muscles attached to hair follicles The hair follicle is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with si ...
muscles, which are responsible for causing hairs to stand up. In humans with little body hair, the effect results in
goose bumps Goose bumps, goosebumps or goose-pimples are the bumps on a person's skin at the base of body hairs which may involuntarily develop when a person is tickled, cold , a common physiological response to cold, aiming to reduce the loss of bo ...

goose bumps
.


Root of the hair

The ''root of the hair'' ends in an enlargement, the ''hair bulb'', which is whiter in color and softer in texture than the shaft and is lodged in a follicular involution of the
epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of animal Animals (also calle ...
called the
hair follicle The hair follicle is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given org ...

hair follicle
. The bulb of hair consists of fibrous connective tissue, glassy membrane, external root sheath, internal root sheath composed of epithelium stratum (
Henle's layer Henle's layer is the third and the outermost layer of the inner root sheath of the hair follicle, consisting of a single layer of cubical cells with clear flattened nuclei. It is named after Germany, German physician, pathologist and anatomist Frie ...
) and granular stratum ( Huxley's layer), cuticle, cortex and medulla.


Natural color

All natural hair colors are the result of two types of hair pigments. Both of these pigments are melanin types, produced inside the hair follicle and packed into granules found in the fibers.
Eumelanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at ...
is the dominant pigment in
brown hair Brown hair is the second most common human hair color Hair color is the pigmentation of hair follicles due to two types of melanin: eumelanin and pheomelanin. Generally, if more melanin is present, the color of the hair is darker; if less me ...

brown hair
and
black hair Black hair is the darkest and most common of all human hair color Hair color is the pigmentation of hair follicles due to two types of melanin: eumelanin and pheomelanin. Generally, if more melanin is present, the color of the hair is darker ...
, while
pheomelanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at ...
is dominant in
red hair Red hair (also known as orange hair and ginger hair) is a hair colour found in one to two percent of the human population Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalit ...

red hair
.
Blond hair Blond or fair hair is a hair color Hair color is the pigmentation of hair follicles due to two types of melanin: eumelanin and pheomelanin. Generally, if more melanin is present, the color of the hair is darker; if less melanin is present, ...
is the result of having little
pigmentation A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes 300px, Yarn drying after being dyed in the early American tradition, at living_history_museum.html"_;"title="Conner_Prairie_living_history_muse ...
in the hair strand.
Gray hair Hair color is the pigmentation of hair follicle The hair follicle is an 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 regul ...
occurs when melanin production decreases or stops, while
poliosis Poliosis (also called poliosis circumscripta), is the decrease or absence of melanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigments found in most organism In biology, an orga ...
is white hair (and often the skin to which the hair is attached), typically in spots that never possessed melanin at all, or ceased for natural reasons, generally genetic, in the first years of life.


Human hair growth

Hair grows everywhere on the external body except for
mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membrane A mucous membrane or mucosa is a biological membrane, membrane that lines various cavities in the body and covers the surface of internal organs. It consists o ...
membranes and glabrous skin, such as that found on the palms of the hands, soles of the feet, and lips. Hair follows a specific growth cycle with three distinct and concurrent phases:
anagen The hair follicle is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given org ...
, catagen, and
telogen The hair follicle is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given org ...
phases; all three occur simultaneously throughout the body. Each has specific characteristics that determine the length of the hair. The body has different types of hair, including
vellus hair Vellus hair is short, thin, light-colored, and barely noticeable hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of g ...
and
androgenic hair Body hair, or androgenic hair, is the terminal hair that develops on the human body during and after puberty. It is differentiated from the head hair and less visible vellus hair, which is much finer and lighter in color. The growth of androgenic ...

androgenic hair
, each with its own type of cellular construction. The different construction gives the hair unique characteristics, serving specific purposes, mainly, warmth and protection.


Texture

Hair exists in a variety of textures. Three main aspects of hair texture are the curl pattern, volume, and consistency. The derivations of hair texture are not fully understood. All mammalian hair is composed of
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin Alpha-keratin, or α-keratin, is a type of keratin Keratin () is one of a family of fibrous structural proteins known as Scleroprot ...

keratin
, so the make-up of
hair follicles The hair follicle is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given org ...

hair follicles
is not the source of varying hair patterns. There are a range of theories pertaining to the curl patterns of hair. Scientists have come to believe that the shape of the
hair shaft Hair is a protein filament that grows from hair follicle, follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick ...
has an effect on the curliness of the individual's hair. A very round shaft allows for fewer
disulfide bonds In biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable ex ...

disulfide bonds
to be present in the hair strand. This means the bonds present are directly in line with one another, resulting in straight hair. The flatter the hair shaft becomes, the curlier hair gets, because the shape allows more
cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the chemical formula, formula HOOC-CH-(NH2)-CH2-SH. The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. The thiol is suscepti ...

cysteine
s to become compacted together resulting in a bent shape that, with every additional disulfide bond, becomes curlier in form. As the hair follicle shape determines curl pattern, the hair follicle size determines thickness. While the circumference of the hair follicle expands, so does the thickness of the hair follicle. An individual's hair volume, as a result, can be thin, normal, or thick. The consistency of hair can almost always be grouped into three categories: fine, medium, and coarse. This trait is determined by the hair follicle volume and the condition of the strand. Fine hair has the smallest circumference, coarse hair has the largest circumference, and medium hair is anywhere between the other two. Coarse hair has a more open cuticle than thin or medium hair causing it to be the most porous.


Classification systems

There are various systems that people use to classify their curl patterns. Being knowledgeable of an individual's hair type is a good start to knowing how to take care of one's hair. There is not just one method to discovering one's hair type. Additionally it is possible, and quite normal to have more than one kind of hair type, for instance having a mixture of both type 3a & 3b curls. ; The Andre Walker Hair Typing System is the most widely used system to classify hair. The system was created by the hairstylist of
Oprah Winfrey Oprah Gail Winfrey (born Orpah Gail Winfrey; January 29, 1954) is an American talk show host, television producer, actress, author, and philanthropist Philanthropy consists of "private initiatives, for the public good, focusing on quali ...

Oprah Winfrey
,
Andre Walker Andre Walker (born August 19, 1956 in Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive map of Chicago , coordinates = , coordinates_footnotes = , subdivision ...
. According to this system there are four types of hair: straight, wavy, curly, kinky. * Type 1 is straight hair, which reflects the most sheen and also the most resilient hair of all of the hair types. It is hard to damage and immensely difficult to curl this hair texture. Because the
sebum A sebaceous gland is a microscopic exocrine Exocrine glands are gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek participle , "setting in motion") is a ...

sebum
easily spreads from the scalp to the ends without curls or kinks to interrupt its path, it is the most oily hair texture of all. * Type 2 is wavy hair, whose texture and sheen ranges somewhere between straight and curly hair. Wavy hair is also more likely to become
frizz Frizz is hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular in ...

frizz
y than straight hair. While type A waves can easily alternate between straight and curly styles, type B and C Wavy hair is resistant to styling. * Type 3 is
curly hair Hair is a protein filament that grows from hair follicle, follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick ...

curly hair
known to have an S-shape. The curl pattern may resemble a lowercase "s", uppercase "S", or sometimes an uppercase "Z" or lowercase "z". This hair type is usually voluminous, "climate dependent (
humidity Humidity is the concentration of water vapor, water vapour present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, d ...

humidity
= frizz), and damage-prone." Lack of proper care causes less defined curls. * Type 4 is
kinky hair Afro-textured hair, or kinky hair is the natural hair texture of certain populations in Africa Africa is the world's second-largest and second-most populous continent A continent is any of several large landmass A landmass, o ...
, which features a tightly coiled curl pattern (or no discernible curl pattern at all) that is often fragile with a very high density. This type of hair shrinks when wet and because it has fewer
cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
layers than other hair types it is more susceptible to damage. ; This is a method which classifies the hair by curl pattern, hair-strand thickness and overall hair volume.


Functions

Many mammals have
fur Fur is a thick growth of hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular bi ...

fur
and other hairs that serve different functions. Hair provides thermal regulation and
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard The leopard (''Pan ...

camouflage
for many animals; for others it provides signals to other animals such as warnings, mating, or other communicative displays; and for some animals hair provides defensive functions and, rarely, even offensive protection. Hair also has a sensory function, extending the sense of touch beyond the surface of the skin. Guard hairs give warnings that may trigger a recoiling reaction.


Warmth

While humans have developed clothing and other means of keeping warm, the hair found on the head serves primarily as a source of heat and cooling (when sweat evaporates from soaked hair) as well as protection from ultra-violet radiation exposure. The function of hair in other locations is debated. Hats and coats are still required while doing outdoor activities in cold weather to prevent
frostbite Frostbite is a skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod ...

frostbite
and
hypothermia Hypothermia is defined as a body core temperature Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal ...
, but the hair on the human body does help to keep the internal temperature regulated. When the body is too cold, the
arrector pili The arrector pili muscles, also knows as hair erector muscles, are small muscles attached to hair follicles The hair follicle is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with si ...
muscles found attached to hair follicles stand up, causing the hair in these follicles to do the same. These hairs then form a heat-trapping layer above the
epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of animal Animals (also calle ...
. This process is formally called
piloerection Goose bumps, goosebumps or goose-pimples are the bumps on a person's skin at the base of body hairs which may involuntarily develop when a person is tickled, cold , a common physiological response to cold, aiming to reduce the loss of bo ...
, derived from the Latin words 'pilus' ('hair') and 'erectio' ('rising up'), but is more commonly known as 'having
goose bumps Goose bumps, goosebumps or goose-pimples are the bumps on a person's skin at the base of body hairs which may involuntarily develop when a person is tickled, cold , a common physiological response to cold, aiming to reduce the loss of bo ...

goose bumps
' in English. This is more effective in other mammals whose fur fluffs up to create air pockets between hairs that insulate the body from the cold. The opposite actions occur when the body is too warm; the arrector muscles make the hair lie flat on the skin which allows heat to leave.


Protection

In some mammals, such as
hedgehog A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphla Eulipotyphla (, which means "truly fat and blind") is an order (biology), order of mammals suggested by molecular methods of phylogenetic reconstruction, and i ...

hedgehog
s and
porcupine Porcupines are large rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% ...

porcupine
s, the hairs have been modified into hard spines or quills. These are covered with thick plates of keratin and serve as protection against predators. Thick hair such as that of the lion's mane and grizzly bear's fur do offer some protection from physical damages such as bites and scratches.


Touch sense

Displacement and vibration of hair shafts are detected by hair follicle nerve receptors and nerve receptors within the skin. Hairs can sense movements of air as well as touch by physical objects and they provide sensory awareness of the presence of
ectoparasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is adaptation (biology), adapted structurally to this w ...
. Some hairs, such as
eyelashes An eyelash (also called lash) (Latin: ''Cilia'') is one of the hairs that grows at the edge of the eyelids. It grows in one layer on the edge of the upper and lower eyelids. Eyelashes protect the eye from debris, dust and small particles and pe ...
, are especially sensitive to the presence of potentially harmful matter.


Eyebrows and eyelashes

The
eyebrow An eyebrow is an area of short hairs above each eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions t ...

eyebrow
s provide moderate protection to the
eye Eyes are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly categorized as parenchyma Parenchyma () is t ...

eye
s from
dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Dust: a general powder of Organic matter, organic or Mineral, ...

dirt
,
sweat Perspiration, also known as sweating, is the production of fluids secreted by the sweat gland Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin Skin is the layer of usually soft, f ...

sweat
and
rain Rain is liquid water in the form of droplet Rain water flux from a canopy. Among the forces that govern drop formation: cohesion, Van der Waals force">Cohesion_(chemistry).html" ;"title="surface tension, Cohesion (chemistry)">cohesion, ...

rain
. They also play a key role in non-verbal
communication Communication (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power o ...

communication
by displaying emotions such as sadness, anger, surprise and excitement. In many other mammals, they contain much longer, whisker-like hairs that act as tactile sensors. The
eyelash An eyelash (also called lash) (Latin: ''Cilia'') is one of the hairs that grows at the edge of the eyelids. It grows in one layer on the edge of the upper and lower eyelids. Eyelashes protect the eye from debris, dust and small particles and pe ...
grows at the edges of the eyelid and protects the eye from dirt. The eyelash is to humans, camels, horses, ostriches etc., what
whiskers Whiskers, more generally called vibrissae (; singular: vibrissa; ), are a type of stiff, functional hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including the ...

whiskers
are to
cat The cat (''Felis catus'') is a domestic Domestic may refer to: In the home * Anything relating to the human home A home, or domicile, is a space used as a permanent or semi-permanent residence for an individual, group or famil ...

cat
s; they are used to sense when dirt,
dust Dust is made of s of solid . On Earth, it generally consists of particles in the that come from various sources such as lifted by wind (an ), , and . Dust in homes is composed of about 20–50% dead . The rest, and in offices, and other ...
, or any other potentially harmful object is too close to the eye. The eye reflexively closes as a result of this
sensation Sensation refers to the processing of the senses by the sensory system; see also ''Sense''. Sensation & perception are not to be confused. Sensation is mostly used as a physiological concept. Perception is when something is perceived. What the latte ...
.


Evolution

Hair has its origins in the common ancestor of mammals, the
synapsid Synapsids are a group of animals that includes mammal Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome ...

synapsid
s, about 300 million years ago. It is currently unknown at what stage the synapsids acquired mammalian characteristics such as
body hair Body hair, or androgenic hair, is the terminal hair that develops on the human body during and after puberty. It is differentiated from the head hair and less visible vellus hair, which is much finer and lighter in color. The growth of androgenic ...
and
mammary gland A mammary gland is an exocrine gland Exocrine glands are gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek participle , "setting in motion") is any m ...
s, as the
fossil A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication used by humans, inc ...

fossil
s only rarely provide direct evidence for soft tissues. Skin impression of the belly and lower tail of a
pelycosaur Pelycosaur ( ) is an older term for basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * B ...
, possibly ''
Haptodus ''Haptodus'' is an extinct Extinction is the termination of a kind of organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chem ...

Haptodus
'' shows the basal synapsid stock bore transverse rows of rectangular
scute A scute or scutum (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...
s, similar to those of a modern
crocodile Crocodiles (family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and of society. I ...

crocodile
, so the age of acquirement of hair logically couldn't have been earlier than ~299 ma, based on the current understanding of the animal's phylogeny. An exceptionally well-preserved skull of '''', a
therapsid Therapsida is a major group of eupelycosauria Eupelycosauria is a large clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic— ...

therapsid
from the
Upper Permian The Permian ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...
, shows smooth, hairless skin with what appears to be glandular depressions, though as a semi-aquatic species it might not have been particularly useful to determine the integument of terrestrial species. The oldest undisputed known fossils showing unambiguous imprints of hair are the
Callovian In the geologic timescale The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth sciences, E ...
(late middle
Jurassic The Jurassic ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...
) ''
Castorocauda ''Castorocauda'' is an extinct, semi-aquatic, beaver Beavers are large, semiaquatic In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, ch ...
'' and several contemporary
haramiyida Haramiyidans were a long lived lineage of Mammaliaformes, mammaliaform cynodonts or mammals. Their teeth, which are by far the most common remains, resemble those of the multituberculates. However, based on ''Haramiyavia'', the jaw is less derive ...
ns, both near-mammal
cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Annum, Ma), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide va ...

cynodont
s, giving the age as no later than ~220 ma based on the modern phylogenetic understanding of these clades. See also the news item at More recently, studies on terminal
Permian The Permian ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...

Russia
n
coprolites A coprolite (also known as a coprolith) is fossilized A fossil (from Classical Latin: , literally 'obtained by digging') is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples inc ...

coprolites
may suggest that non-mammalian synapsids from that era had fur. If this is the case, these are the oldest hair remnants known, showcasing that fur occurred as far back as the latest
Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Eu ...
. Some modern mammals have a special gland in front of each
orbit In celestial mechanics, an orbit is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificial satellite around an object or po ...
used to preen the fur, called the
harderian gland The Harderian gland is a gland found within the eye's orbit In celestial mechanics, an orbit is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or ...
. Imprints of this structure are found in the skull of the small early mammals like ''
Morganucodon ''Morganucodon'' ("Glamorgan tooth") is an early mammaliaform genus that lived from the Late Triassic to the Middle Jurassic. It first appeared about 205 million years ago. Unlike many other early mammaliaforms, ''Morganucodon'' is well represent ...

Morganucodon
'', but not in their
cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Annum, Ma), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide va ...

cynodont
ancestors like ''
Thrinaxodon ''Thrinaxodon'' is an extinct genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may als ...

Thrinaxodon
''. The hairs of the fur in modern animals are all connected to nerves, and so the fur also serves as a transmitter for sensory input. Fur could have evolved from sensory hair (whiskers). The signals from this sensory apparatus is interpreted in the
neocortex The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class ...

neocortex
, a section of the brain that expanded markedly in animals like ''Morganucodon'' and ''
Hadrocodium ''Hadrocodium wui'' is an extinct Mammaliaformes, mammaliaform that lived during the Sinemurian stage of the Early Jurassic approximately in the Lufeng Formation of the Lufeng Basin in what is now the Yunnan province in south-western China (, pa ...
''. The more advanced therapsids could have had a combination of naked skin,
whisker Whiskers, more generally called vibrissae (; singular: vibrissa; ), are a type of stiff, functional hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including th ...

whisker
s, and
scute A scute or scutum (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...
s. A full
pelage Fur is a thick growth of hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular b ...

pelage
likely did not evolve until the therapsid-mammal transition. The more advanced, smaller therapsids could have had a combination of hair and scutes, a combination still found in some modern mammals, such as
rodents Rodents (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republi ...

rodents
and the
opossum Opossums () are members of the marsupial Order (biology), order Didelphimorphia () Endemism, endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 120+ species in 19 Genus, genera. Opossums originated i ...

opossum
. The high interspecific variability of the size, color, and microstructure of hair often enables the identification of species based on single hair filaments. In varying degrees most
mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
s have some skin areas without natural hair. On the human body, glabrous
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differ ...

skin
is found on the
ventral Standard anatomical terms of location deal unambiguously with the of s, including s. Terms used generally derive from or roots and used to describe something in its . This position provides a definition of what is at the front ("anterior"), be ...

ventral
portion of the
finger A finger is a limb of the body and a type of digit (anatomy), digit, an organ of wikt:manipulate, manipulation and Wikt:sensation, sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrat ...

finger
s, , soles of feet and
lips Lips are a visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be an ...
, which are all parts of the body most closely associated with interacting with the world around us, as are the
labia minora The labia minora (Latin for ''smaller lips,'' singular: ''labium minus'' "smaller lip"), also known as the inner labia, inner lips, vaginal lips or nymphae, are two flaps of skin on either side of the human Humans (''Homo sapiens'') are th ...

labia minora
and
glans penis The glans penis, commonly referred to as the glans, is a structure at the distal Standard anatomical terms of location deal unambiguously with the anatomy of animals, including humans. Terms used generally derive from Latin or Greek language ...

glans penis
. There are four main types of
mechanoreceptor A mechanoreceptor, also called mechanoceptor, is a sensory receptor Sensory neurons, also known as afferent neurons, are neuron A neuron or nerve cell is an electrically excitable cell Cell most often refers to: * Cell (biology), the fu ...
s in the glabrous skin of humans:
Pacinian corpuscles Pacinian corpuscle or lamellar corpuscle or Vater-Pacini corpuscle; is one of the four major types of mechanoreceptors A mechanoreceptor, also called mechanoceptor, is a sensory receptor Sensory neurons, also known as afferent neurons, are n ...
,
Meissner's corpuscles Tactile corpuscles or Meissner's corpuscles are a type of mechanoreceptor discovered by anatomy, anatomist Georg Meissner (1829–1905) and Rudolf Wagner. This corpuscle is a type of nerve ending in the skin that is responsible for sensitivity to li ...
,
Merkel's discs Merkel nerve endings are mechanoreceptors, a type of sensory receptor, that are found in the basal epidermis and hair follicles. They are nerve endings and provide information on mechanical pressure, position, and deep static touch features, such a ...
, and
Ruffini corpuscles The Bulbous corpuscle or Ruffini ending or Ruffini corpuscle is a slowly adapting mechanoreceptor located in the skin, cutaneous tissue between the dermal papillae and the hypodermis. It is named after Angelo Ruffini. Structure Ruffini corpuscles a ...
. The
naked mole-rat The naked mole-rat (''Heterocephalus glaber''), also known as the sand puppy, is a burrowing rodent native to parts of East Africa East Africa, Eastern Africa, or East of Africa is the eastern sub-region A subregion is a part of a larger ...
(''Heterocephalus glaber'') has evolved skin lacking in general, pelagic hair covering, yet has retained long, very sparsely scattered tactile hairs over its body. Glabrousness is a trait that may be associated with
neoteny Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the Physiology, physiological (or Somatic (biology), somatic) development of an organism, typically an animal. Neoteny is ...

neoteny
.


Human hairlessness

The general hairlessness of humans in comparison 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. On an individual basis, mutations in the gene HR can lead to complete hair loss, though this is not typical in humans. Humans may also lose their hair as a result of hormonal imbalance due to drugs or pregnancy. In order to comprehend why humans have significantly less body hair than other primates, one must understand that mammalian body hair is not merely an aesthetic characteristic; it protects the skin from wounds, bites, heat, cold, and UV radiation. Additionally, it can be used as a communication tool and as a camouflage. Humans are the only primate species that have undergone significant hair loss and of the approximately 5000 extant species of mammal, only a handful are effectively hairless. This list includes elephants, rhinoceroses, hippopotamuses, walruses, some species of
pig The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous An omnivore () is an animal that has the ability to eat and survive on both plant and ani ...

pig
s, whales and other
cetaceans Cetaceans (from la, cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus (mythology), Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the ...

cetaceans
, and naked mole rats. Most mammals have light skin that is covered by fur, and biologists believe that early human ancestors started out this way also. Dark skin probably evolved after humans lost their body fur, because the naked skin was vulnerable to the strong
UV radiation Ultraviolet (UV) is a form of electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that stud ...
as explained in the
Out of Africa hypothesis upright=1.5, Expansion of early modern humans from Africa through the Near East In paleoanthropology Paleoanthropology or paleo-anthropology is a branch of paleontology and biological anthropology, anthropology which seeks to understand t ...
. Therefore, evidence of the time when human skin darkened has been used to date the loss of human body hair, assuming that the dark skin was needed after the fur was gone. It was expected that dating the split of the ancestral human louse into two species, the
head louse The head louse (''Pediculus humanus capitis'') is an obligate parasite, obligate parasitism, ectoparasite of humans. Head lice are wingless insects that spend their entire lives on the human scalp and feeding exclusively on human blood. Humans ...

head louse
and the pubic louse, would date the loss of body hair in human ancestors. However, it turned out that the human pubic louse does not descend from the ancestral human louse, but from the gorilla louse, diverging 3.3 million years ago. This suggests that humans had lost body hair (but retained head hair) and developed thick pubic hair prior to this date, were living in or close to the forest where gorillas lived, and acquired pubic lice from butchering gorillas or sleeping in their nests. The evolution of the
body louse The body louse (''Pediculus humanus humanus'', also known as ''Pediculus humanus corporis'') is a hematophagic ectoparasite Parasitism is a symbiotic relationship between species In biology, a species is the basic unit of biologic ...
from the head louse, on the other hand, places the date of clothing much later, some 100,000 years ago. The sweat glands in humans could have evolved to spread from the hands and feet as the body hair changed, or the hair change could have occurred to facilitate sweating.
Horse The horse (''Equus ferus caballus'') is a domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to ...

Horse
s and humans are two of the few animals capable of sweating on most of their body, yet horses are larger and still have fully developed fur. In humans, the skin hairs lie flat in hot conditions, as the arrector pili muscles relax, preventing heat from being trapped by a layer of still air between the hairs, and increasing heat loss by
convection Convection is single or multiphase fluid flow that occurs Spontaneous process, spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When t ...

convection
. Another hypothesis for the thick
body hair Body hair, or androgenic hair, is the terminal hair that develops on the human body during and after puberty. It is differentiated from the head hair and less visible vellus hair, which is much finer and lighter in color. The growth of androgenic ...
on humans proposes that
Fisherian runaway Fisherian runaway or runaway selection is a sexual selection Sexual selection is a mode of natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right ...
sexual selection Sexual selection is a mode of natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrat ...
played a role (as well as in the selection of long head hair), (see terminal and
vellus hair Vellus hair is short, thin, light-colored, and barely noticeable hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of g ...
), as well as a much larger role of testosterone in men. Sexual selection is the only theory thus far that explains the
sexual dimorphism Sexual dimorphism is the condition where the sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in ...
seen in the hair patterns of men and women. On average, men have more
body hair Body hair, or androgenic hair, is the terminal hair that develops on the human body during and after puberty. It is differentiated from the head hair and less visible vellus hair, which is much finer and lighter in color. The growth of androgenic ...

body hair
than women. Males have more
terminal hair In humans, terminal hair is thick and long, such as what grows on the scalp, as compared with vellus hair Vellus hair is short, thin, light-colored, and barely noticeable hair Hair is a protein filament that grows from follicles foun ...
, especially on the
face The face is the front of an animal's head that features the eyes Eyes are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's ti ...
,
chest The thorax or chest is a part of the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανι ...
,
abdomen The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the Trunk (anatomy) ...
, and back, and females have more
vellus hair Vellus hair is short, thin, light-colored, and barely noticeable hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of g ...
, which is less visible. The halting of hair development at a juvenile stage, vellus hair, would also be consistent with the
neoteny Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the Physiology, physiological (or Somatic (biology), somatic) development of an organism, typically an animal. Neoteny is ...

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. A further hypothesis is that human hair was reduced in response to
ectoparasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is adaptation (biology), adapted structurally to this w ...
. The "ectoparasite" explanation of modern human nakedness is based on the principle that a hairless primate would harbor fewer parasites. When our ancestors adopted group-dwelling social arrangements roughly 1.8 mya, ectoparasite loads increased dramatically. Early humans became the only one of the 193 primate species to have
fleas Flea, the common name for the order (biology), order Siphonaptera, includes 2,500 species of small flightless insects that survive as external parasitism, parasites of mammals and birds. Fleas live by consuming blood, or hematophagy, from the ...
, which can be attributed to the close living arrangements of large groups of individuals. While primate species have communal sleeping arrangements, these groups are always on the move and thus are less likely to harbor ectoparasites. Another view is proposed by James Giles, who attempts to explain hairlessness as evolved from the relationship between mother and child, and as a consequence of
bipedalism Bipedalism is a form of terrestrial locomotion Terrestrial locomotion has evolved Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from ...

bipedalism
. Giles also connects romantic love to hairlessness. Another hypothesis is that humans' use of fire caused or initiated the reduction in human hair.


Evolutionary variation

Evolutionary biologists suggest that the genus ''
Homo ''Homo'' () is the genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), cir ...

Homo
'' arose in
East Africa East Africa, Eastern Africa, or East of Africa is the eastern sub-region A subregion is a part of a larger region or continent and is usually based on location. Cardinal directions, such as south or southern, are commonly used to define a subr ...
approximately 2.5 million years ago. They devised new hunting techniques. The higher protein diet led to the evolution of larger body and brain sizes. Jablonski postulates that increasing body size, in conjunction with intensified hunting during the day at the equator, gave rise to a greater need to rapidly expel heat. As a result, humans evolved the ability to sweat: a process which was facilitated by the loss of body hair. Another factor in human evolution that also occurred in the prehistoric past was a preferential selection for
neoteny Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the Physiology, physiological (or Somatic (biology), somatic) development of an organism, typically an animal. Neoteny is ...

neoteny
, particularly in females. The idea that adult humans exhibit certain neotenous (juvenile) features, not evinced in the other great apes, is about a century old.
Louis Bolk Lodewijk 'Louis' Bolk (December 10, 1866, Rotterdam, Overschie – June 17, 1930, Amsterdam) was a Netherlands, Dutch Anatomy, anatomist who created the fetalization theory about the human body. It states that when a human being is born, it ...
made a long list of such traits, and
Stephen Jay Gould Stephen Jay Gould (; September 10, 1941 – May 20, 2002) was an American paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start ...
published a short list in ''
Ontogeny and Phylogeny ''Ontogeny and Phylogeny'' is a 1977 book on evolution by Stephen Jay Gould Stephen Jay Gould (; September 10, 1941 – May 20, 2002) was an American paleontologist Paleontology (), also spelled palaeontology or palæontology, is the sc ...
''. In addition,
paedomorphic Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the Physiology, physiological (or Somatic (biology), somatic) development of an organism, typically an animal. Neoteny is ...
characteristics in women are often acknowledged as desirable by men in
developed countries A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state A sovereign state is a political entity A polity is an identifiable political entity ...
. For instance,
vellus hair Vellus hair is short, thin, light-colored, and barely noticeable hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of g ...
is a juvenile characteristic. However, while men develop longer, coarser, thicker, and darker
terminal hair In humans, terminal hair is thick and long, such as what grows on the scalp, as compared with vellus hair Vellus hair is short, thin, light-colored, and barely noticeable hair Hair is a protein filament that grows from follicles foun ...
through
sexual differentiation Sexual differentiation is the process of development of the sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete ...
, women do not, leaving their vellus hair visible.


Texture


Curly 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 Ultraviolet (UV) is a form of with from 10 (with a corresponding frequency around 30 ) to 400 nm (750 ), shorter than that of , but longer than s. UV radiation is present in , and constitutes about 10% of the total electromagnetic radi ...
. 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 Afro-textured hair, or kinky hair is the natural hair texture of certain populations in Africa and the African diaspora. Despite its name, this hair texture is also found in some parts of Oceania and Southeast Asia. Each strand of this hair type g ...
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). It is substantiated by Iyengar's findings (1998) that UV light can enter into straight human hair roots (and thus into the body through the skin) via the hair shaft. Specifically, the results of that study suggest that this phenomenon resembles the passage of light through fiber optic tubes (which do not function as effectively when kinked or sharply curved or coiled). In this sense, when hominids (i.e. Homo Erectus) were gradually losing their straight body hair and thereby exposing the initially pale skin underneath their fur to the sun, straight hair would have been an adaptive liability. By inverse logic, later, as humans traveled farther from Africa and/or the equator, straight hair may have (initially) evolved to aid the entry of UV light into the body during the transition from dark, UV-protected skin to paler skin. Jablonski's assertions suggest that the adjective "woolly" in reference to Afro-hair is a
misnomer A misnomer is a name that is incorrectly or unsuitably applied. Misnomers often arise because something was named long before its correct nature was known, or because an earlier form of something has been replaced by a later form to which the na ...
in connoting the high heat insulation derivable from the true wool of sheep. Instead, the relatively sparse density of Afro-hair, combined with its springy coils actually results in an airy, almost sponge-like structure that in turn, Jablonski argues, more likely facilitates an increase in the circulation of cool air onto the scalp. Further, wet Afro-hair does not stick to the neck and scalp unless totally drenched and instead tends to retain its basic springy puffiness because it less easily responds to moisture and sweat than straight hair does. In this sense, the trait may enhance comfort levels in intense equatorial climates more than straight hair (which, on the other hand, tends to naturally fall over the ears and neck to a degree that provides slightly enhanced comfort levels in cold climates relative to tightly coiled 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 Afro-textured hair, or kinky hair is the natural hair texture of certain populations in Africa and the African diaspora. Despite its name, this hair texture is also found in some parts of Oceania and Southeast Asia. Each strand of this hair type g ...
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.


The EDAR locus

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 Afro-textured hair, or kinky hair is the natural hair texture of certain populations in Africa and the African diaspora. Despite its name, this hair texture is also found in some parts of Oceania and Southeast Asia. Each strand of this hair type g ...
. 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.


Disease

Ringworm Dermatophytosis, also known as ringworm, is a fungal infection Mycosis is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and ...

Ringworm
is a
fungal disease A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...
that targets hairy skin. Premature greying of hair is another condition that results in greying before the age of 20 years in Whites, before 25 years in Asians, and before 30 years in Africans.


Hair care

Hair care involves the
hygiene Hygiene is a series of practices performed to preserve health Health, according to the World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies a ...

hygiene
and
cosmetology Cosmetology (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxim ...
of hair including hair on the
scalp The scalp is the anatomical area bordered by the human face The face is the front of an animal's head that features the eyes Eyes are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on ...
, facial hair (
beard A beard is the hair that grows on the jaw, chin, upper lip, lower lip, cheeks, and neck of humans and some non-human animals. In humans, usually only pubescent or adult males are able to grow beards. Some women with hirsutism Hirsutism is e ...

beard
and
moustache A moustache (; en-US, mustache, ) is a strip of facial hair grown above the upper lip. Moustaches have been worn in various styles throughout history. Etymology The word "moustache" is French language, French, and is derived from the Itali ...

moustache
),
pubic hair Pubic hair is terminal body hair that is found in the genital area of adolescent and adult humans. The hair is located on and around the sex organs and sometimes at the top of the inside of the thighs. In the pubic region around the pubis ...

pubic hair
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.


Removal practices

Depilation Hair removal, also known as epilation or depilation, is the deliberate removal of body hair. 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 ha ...
is the removal of hair from the surface of the skin. This can be achieved through methods such as
shaving Shaving is the removal of hair, by using a razor A razor is a blade A blade is the portion of a tool, weapon, or machine with an edge that is designed to wikt:puncture, puncture, wikt:chop, chop, Cutting, slice or scraper (archaeology), ...

shaving
.
Epilation Hair removal, also known as epilation or depilation, is the deliberate removal of body hair. Hair typically grows all over the human body. Hair can become more visible during and after puberty Puberty is the process of physical changes thr ...
is the removal of the entire hair strand, including the part of the hair that has not yet left the follicle. A popular way to epilate hair is through
waxing Waxing is the process of hair removal Hair removal, also known as epilation or depilation, is the deliberate removal of body hair or head hair. Hair typically grows all over the human body and can vary in thickness and length across human ...

waxing
.


Shaving

Shaving Shaving is the removal of hair, by using a razor A razor is a blade A blade is the portion of a tool, weapon, or machine with an edge that is designed to wikt:puncture, puncture, wikt:chop, chop, Cutting, slice or scraper (archaeology), ...

Shaving
is accomplished with bladed instruments, such as
razors A razor is a blade A blade is the portion of a tool, weapon, or machine with an edge that is designed to wikt:puncture, puncture, wikt:chop, chop, Cutting, slice or scraper (archaeology), scrape surfaces or materials. Blades are typically mad ...
. The
blade A blade is the portion of a tool A tool is an object that can extend an individual's ability to modify features of the surrounding environment. Although many animals use tool use by animals, simple tools, only human beings, whose use of st ...

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 The lower face of a man sporting designer stubble Designer stubble is a facial hair style which is a short growth of beard, aimed to effect a rugged masculine or deliberately unkempt appearance. Initially made popular in the 1980s by singer Georg ...
after having shaved their faces. This new growth is called . 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.


Waxing

Waxing Waxing is the process of hair removal Hair removal, also known as epilation or depilation, is the deliberate removal of body hair or head hair. Hair typically grows all over the human body and can vary in thickness and length across human ...

Waxing
involves using a sticky wax and strip of paper or cloth to pull hair from the root. Waxing is the ideal hair removal technique to keep an area hair-free for long periods of time. It can take three to five weeks for waxed hair to begin to resurface again. Hair in areas that have been waxed consistently is known to grow back finer and thinner, especially compared to hair that has been shaved with a razor.


Laser removal

Laser hair removal is a cosmetic method where a small
laser A laser is a device that emits light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as h ...

laser
beam pulses selective heat on dark target matter in the area that causes hair growth without harming the skin tissue. This process is repeated several times over the course of many months to a couple of years with hair regrowing less frequently until it finally stops; this is used as a more permanent solution to
waxing Waxing is the process of hair removal Hair removal, also known as epilation or depilation, is the deliberate removal of body hair or head hair. Hair typically grows all over the human body and can vary in thickness and length across human ...

waxing
or
shaving Shaving is the removal of hair, by using a razor A razor is a blade A blade is the portion of a tool, weapon, or machine with an edge that is designed to wikt:puncture, puncture, wikt:chop, chop, Cutting, slice or scraper (archaeology), ...

shaving
. Laser removal is practiced in many clinics along with many at-home products.


Cutting and trimming

Because the hair on one's head is normally longer than other types of body hair, it is cut with
scissors Scissors are hand-operated shearing tools. A pair of scissors consists of a pair of metal blades pivoted so that the sharpened edges slide against each other when the handles (bows) opposite to the pivot are closed. Scissors are used for cutti ...

scissors
or
clippers A clipper is fast sailing vessel, generally from the 19th century. Clipper or clippers may also refer to: Business * Clipper Logistics, a British logistics company * Clipper Teas, branded as "Clipper", a British, fairtrade tea company * Clipper ...

clippers
. People with longer hair will most often use scissors to cut their hair, whereas shorter hair is maintained using a trimmer. Depending on the desired length and overall health of the hair, periods without cutting or trimming the hair can vary. Cut hair may be used in
wig A wig is a head or hair accessory made from human hair, animal hair, or synthetic fiber. The word wig is short for periwig, which makes its earliest known appearance in the English language in William Shakespeare's ''The Two Gentlemen of Verona' ...

wig
s. Global imports of hair in 2010 was worth $US 1.24 billion.


Social role

Hair has great social significance for
human being Humans (''Homo sapiens'') are the most abundant and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A speci ...
s. It can grow on most external areas of the
human body The human body is the structure of a Human, human being. It is composed of many different types of Cell (biology), cells that together create Tissue (biology), tissues and subsequently organ systems. They ensure homeostasis and the life, viabi ...

human body
, except on the palms of the
hand A hand is a prehensile, multi- fingered appendage located at the end of the forearm The forearm is the region of the upper limb between the Elbow-joint, elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, ...

hand
s and the soles of the feet (among other areas). Hair is most noticeable on most people in a small number of areas, which are also the ones that are most commonly trimmed, plucked, or . These include the
face The face is the front of an animal's head that features the eyes Eyes are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's ti ...

face
,
ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is the external part of the ear, which consists ...

ear
s,
head Head Sport GmbH is an American-Austrian manufacturing company Manufacturing is the creation or production Production may be: Economics and business * Production (economics) * Production, the act of manufacturing goods * Production, in th ...

head
, eyebrows,
leg A leg is a weight-bearingIn orthopedics Orthopedic surgery or orthopedics, is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat muscul ...
s, and
armpit The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the joint where the arm connects to the shoulder. It also contains many sweat glands. In humans, the formation of body odor happens mostly in the armpit. ...

armpit
s, as well as the
pubic region The hypogastrium (also called the hypogastric region or suprapubic region) is a region of the abdomen located below the umbilical region The umbilical region, is one of the Quadrants and regions of abdomen#Regions, nine regions of the abdomen. ...
. The highly visible differences between male and female body and facial hair are a notable
secondary sex characteristic Secondary sex characteristics are features that appear during puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most ab ...
. The world's longest documented hair belongs to Xie Qiuping (in
China China (), officially the People's Republic of China (PRC; ), is a country in East Asia East Asia is the eastern region of Asia Asia () is Earth's largest and most populous continent, located primarily in the Eastern Hemisphere ...

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.


Indication of status

Healthy hair indicates health and youth (important in
evolutionary biology Evolutionary biology is the subfield of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interacti ...
). Hair color and texture can be a sign of ethnic ancestry.
Facial hair Facial hair is hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molec ...
is a sign of
puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natur ...

puberty
in men. White or gray hair is a sign of age or genetics, which may be concealed with
hair dye Hair coloring, or hair dyeing, is the practice of changing the hair color. The main reasons for this are beauty, cosmetic: to cover Gray hair, gray or white hair, to change to a color regarded as more fashionable or desirable, or to restore the orig ...
(not easily for some), although many prefer to assume it (especially if it is a
poliosis Poliosis (also called poliosis circumscripta), is the decrease or absence of melanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigments found in most organism In biology, an orga ...
characteristic of the person since childhood). Male pattern
baldness Hair loss, also known as alopecia or baldness, refers to a loss of hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, ...
is a sign of age, which may be concealed with a toupee, hats, or religious and cultural adornments. Although drugs and medical procedures exist for the treatment of baldness, many balding men simply shave their heads. In early modern China, the queue was a male hairstyle worn by the Manchus from central Manchuria and the Han Chinese during the Qing dynasty; hair on the front of the head was shaved off above the temples every ten days, mimicking male-pattern baldness, and the rest of the hair braided into a long pigtail.
Hairstyle A hairstyle, hairdo, haircut or coiffure refers to the fashion, styling of hair, usually on the human scalp. Sometimes, this could also mean an editing of facial or body hair. The fashioning of hair can be considered an aspect of personal ...

Hairstyle
may be an indicator of group membership. During the
English Civil War The English Civil War (1642–1651) was a series of civil wars A civil war, also known as an intrastate war in polemology, is a war War is an intense armed conflict between states State may refer to: Arts, entertainment, ...
, the followers of
Oliver Cromwell Oliver Cromwell (25 April 15993 September 1658) was an English general and statesman who, first as a subordinate and later as Commander-in-Chief, led armies An army (from Latin ''arma'' "arms, weapons" via Old French ''armée'', "armed" e ...

Oliver Cromwell
decided to crop their hair close to their head, as an act of defiance to the curls and ringlets of the king's men. This led to the Parliamentary faction being nicknamed
Roundhead Roundheads were the supporters of the Parliament of England during the English Civil War (1642–1651). Also known as Parliamentarians, they fought against King Charles I of England and his supporters, known as the Cavaliers or Royalists, who ...
s. Recent isotopic analysis of hair is helping to shed further light on sociocultural interaction, giving information on food procurement and consumption in the 19th century. Having
bobbed hair A bob cut, also known as a bob (also bob: the university of sioux falls football complex), is a short length haircut, in which the hair is typically cut straight around the head at about jaw-level, often with a fringe (hair), fringe (or "bangs") ...

bobbed hair
was popular among the
flapper Flappers were a subculture A subculture is a group of people within a culture Culture () is an umbrella term which encompasses the social behavior and Norm (social), norms found in human Society, societies, as well as the knowledge, b ...

flapper
s in the 1920s as a sign of rebellion against traditional roles for women. Female art students known as the "cropheads" also adopted the style, notably at the Slade School in London, England. Regional variations in
hirsutism Hirsutism is excessive body hair on parts of the body where hair is normally absent or minimal. The word is from early 17th century: from Latin ''hirsutus'' meaning "hairy". It may refer to a "male" pattern of hair growth that may be a sign of a ...
cause practices regarding hair on the arms and legs to differ. Some religious groups may follow certain rules regarding hair as part of religious observance. The rules often differ for men and women. Many subcultures have hairstyles which may indicate an unofficial membership. Many
hippie A hippie, also spelled hippy, especially in UK English, was a member of the counterculture of the 1960s The counterculture of the 1960s was an anti-establishment An anti-establishment view or belief is one which stands in opposition ...

hippie
s, metalheads, and Indian
sadhus ''Sadhu'' (IAST The International Alphabet of Sanskrit Transliteration (IAST) is a transliteration scheme that allows the lossless romanisation Romanization or romanisation, in linguistics Linguistics is the science, scientif ...

sadhus
have
long hair 'Long hair'' is a hairstyle where the head hair is allowed to grow to a considerable length. Exactly what constitutes long hair can change from culture to culture, or even within cultures. For example, a woman with chin-length hair in some cultu ...

long hair
, as well many older indie kids. Many punks wear a hairstyle known as a
mohawkMohawk may refer to: Related to Native Americans *Mohawk people, an indigenous people of North America (Canada and New York) *Mohawk language, the language spoken by the Mohawk people *Mohawk hairstyle, from a hairstyle once thought to have been tr ...
or other spiked and dyed hairstyles;
skinhead A skinhead is a member of a subculture which originated among working class The working class (or labouring class) comprises those engaged in manual-labour occupations or industrial work, who are remunerated via waged or salaried con ...

skinhead
s have short-cropped or completely shaved heads. Long stylized bangs were very common for
emo Emo is a rock music Rock music is a broad genre of popular music Popular music is music with wide appeal that is typically distributed to large audiences through the music industry. These forms and styles can be enjoyed and performe ...
s, scene kids and younger indie kids in the 2000s and early 2010s, among people of both
gender Gender is the range of characteristics pertaining to, and differentiating between femininity Femininity (also called womanliness or girlishness) is a set of attributes, behaviors, and roles generally associated with women A woman is ...

gender
s. Heads were shaved in
concentration camp Internment is the imprisonment of people, commonly in large groups, without charges or intent to file charges. The term is especially used for the confinement "of enemy citizens in war War is an intense armed conflict between state ...
s, and head-shaving has been used as
punishment Punishment, commonly, is the imposition of an undesirable or unpleasant outcome upon a group or individual, meted out by an authority In the fields of sociology Sociology is the study of society, human social behaviour, patterns of soci ...

punishment
, especially for women with long hair. The shaven head is common in
military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare War is an intense armed conflict between State (polity), states, governments, Society, societies, or pa ...

military
haircuts, while Western monks are known for the
tonsure Tonsure () is the practice of cutting or shaving some or all of the hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Bioch ...

tonsure
. By contrast, among some Indian holy men, the hair is worn extremely long. In the time of Confucius (5th century BCE), the Chinese grew out their hair and often tied it, as a symbol of filial piety. Regular hairdressing in some cultures is considered a sign of wealth or status. The
dreadlocks Dreadlocks, also locs, dreads, or in Sanskrit Sanskrit (; attributively , ; , , ) is a of that belongs to the branch of the . It arose in South Asia after its predecessor languages had there from the northwest in the late . Sanskrit ...
of the
Rastafari movement Rastafari, also known as the Rastafari movement or Rastafarianism, is a religion Religion is a social Social organisms, including humans, live collectively in interacting populations. This interaction is considered social whether they ...
were despised early in the movement's history. In some cultures, having one's hair cut can symbolize a liberation from one's past, usually after a trying time in one's life. Cutting the hair also may be a sign of mourning. Tightly coiled hair in its natural state may be worn in an
Afro An afro is a natural growth of curly textured hair, in any length kinky hair texture (also known as a natural), or specifically styled with chemical curling products by individuals with naturally curly Curly or Curley is a surname, given name ...

Afro
. This hairstyle was once worn among
African American African Americans (also referred to as Black Americans or Afro-Americans) are an ethnic group An ethnic group or ethnicity is a grouping of people A people is any plurality of person A person (plural people or persons) is a being t ...

African American
s as a symbol of racial pride. Given that the coiled texture is the natural state of some African Americans' hair, or perceived as being more "African", this simple style is now often seen as a sign of self-acceptance and an affirmation that the beauty norms of the (
eurocentric Eurocentrism (also Eurocentricity or Western-centrism) is a World view, worldview that is centred on Western culture, Western civilisation or a biased view that favours it over non-Western civilisations. The exact scope of Eurocentrism varies f ...
) dominant culture are not absolute. It is important to note that African Americans as a whole have a variety of hair textures, as they are not an ethnically homogeneous group, but an ad-hoc of different racial admixtures. The film ''
Easy Rider ''Easy Rider'' is a 1969 American independent Independent or Independents may refer to: Arts, entertainment, and media Artist groups * Independents (artist group), a group of modernist painters based in the New Hope, Pennsylvania, area of the ...
'' (1969) includes the assumption that the two main characters could have their long hairs forcibly shaved with a rusty razor when jailed, symbolizing the intolerance of some conservative groups toward members of the
counterculture A counterculture is a culture Culture () is an umbrella term which encompasses the social behavior and Norm (social), norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilitie ...
. At the conclusion of the Oz obscenity trials in the UK in 1971, the defendants had their heads shaved by the police, causing public outcry. During the appeal trial, they appeared in the dock wearing wigs. A case where a 14-year-old student was expelled from school in
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At 8.5 million square kilometers (3.2 million square miles) and with over 211 mill ...

Brazil
in the mid-2000s, allegedly because of his fauxhawk haircut, sparked national debate and legal action resulting in compensation.


Religious practices

Women's hair may be hidden using
headscarves File:Martin Kober 002.jpg, In Christian cultures nuns cover their body and hair. Here an example of a 16th century wimple, worn by a widowed Queen Anna of Poland, with veil and a ruff (clothing), ruff around the neck., alt=The robe of a nun which ...

headscarves
, a common part of the ''
hijab A hijab (; ar, حجاب, translit=ḥijāb, in common English usage) is a veil A veil is an article of clothing or hanging cloth that is intended to cover some part of the head Head Sport GmbH is an American-Austrian manufacturing compan ...

hijab
'' in
Islam Islam (; ar, اَلْإِسْلَامُ, al-’Islām, "submission o God Oh God may refer to: * An exclamation; similar to "oh no", "oh yes", "oh my", "aw goodness", "ah gosh", "ah gawd"; see interjection An interjection is a word or ex ...
and a symbol of modesty required for certain religious rituals in
Eastern Orthodoxy The Eastern Orthodox Church, also called the Orthodox Church, is the List of Christian denominations by number of members, second-largest Christian church, with approximately 220 million baptised members. It operates as a Communion (Christ ...
.
Russian Orthodox Church , native_name_lang = ru , image = Moscow July 2011-7a.jpg , imagewidth = , alt = , caption = Cathedral of Christ the Saviour The Cathedral of Christ the Saviour ( rus, Храм Хр ...

Russian Orthodox Church
requires all married women to wear headscarves inside the church; this tradition is often extended to all women, regardless of marital status.
Orthodox Judaism Orthodox Judaism is the collective term for the traditionalist branches of contemporary Judaism Judaism is an Abrahamic religions, Abrahamic, monotheism, monotheistic, and ethnic religion comprising the collective religious, cultural, ...
also commands the use of scarves and other head coverings for married women for modesty reasons. Certain
Hindu Hindus (; ) are persons who regard themselves as culturally, ethnically, or religiously adhering to aspects of Hinduism Hinduism () is an Indian religion Indian religions, sometimes also termed Dharmic religions or Indic re ...

Hindu
sects also wear head scarves for religious reasons.
Sikhs Sikhs ( or ; pa, ਸਿੱਖ, ', ) are people who adhere to Sikhism, a monotheistic religion that originated in the late 15th century '' by Francisco Pradilla Ortiz, 1882: Muhammad XII surrenders to Ferdinand and Isabella The 15th ...
have an obligation not to cut hair (a Sikh cutting hair becomes 'apostate' which means fallen from religion) and men keep it tied in a bun on the head, which is then covered appropriately using a
turban A turban (from Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, Persian people, the majority ethnic group in Iran, not to be conflated with the Iranian peoples ** Per ...

turban
. Multiple religions, both ancient and contemporary, require or advise one to allow their hair to become
dreadlocks Dreadlocks, also locs, dreads, or in Sanskrit Sanskrit (; attributively , ; , , ) is a of that belongs to the branch of the . It arose in South Asia after its predecessor languages had there from the northwest in the late . Sanskrit ...
, though people also wear them for fashion. For men, Islam, Orthodox Judaism, Orthodox Christianity, Roman Catholicism, and other religious groups have at various times recommended or required the covering of the head and sections of the hair of men, and some have dictates relating to the cutting of men's facial and head hair. Some Christian sects throughout history and up to modern times have also religiously proscribed the cutting of women's hair. For some
Sunni Sunni Islam () is by far the largest branch Image:Tree Leaves.JPG, The branches and leaves of a tree. A branch ( or , ) or tree branch (sometimes referred to in botany as a ramus) is a woody structural member connected to but not part o ...
madhab A ' ( ar, مذهب ', , "way to act") is a school of thought within ''fiqh ''Fiqh'' (; ar} ) is Islamic jurisprudence. Muhammad-> Sahabah, Companions-> Tabi‘un, Followers-> Fiqh. The commands and prohibitions chosen by God were revealed ...
s, the donning of a
kufi A kufi or kufi cap is a brimless, short, and rounded cap A cap is a kind of soft and flat headgear, usually with a visor. Caps have crowns that fit very close to the head. They made their first appearance as early as 3,200BC. Caps typically h ...

kufi
or
topi ''Damaliscus lunatus jimela'' is a subspecies In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical ...
is a form of
sunnah In Islam Islam (; ar, اَلْإِسْلَامُ, al-’Islām, "submission o God Oh God may refer to: * An exclamation; similar to "oh no", "oh yes", "oh my", "aw goodness", "ah gosh", "ah gawd"; see interjection An interjection i ...
.The War Within Our Hearts – Page 65 Sa'ad Quadri – 2013


See also

* Chaetophobia – the fear of hair *
Hair analysis (alternative medicine) In mainstream scientific usage, hair analysis is the chemical analysis of a hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart fr ...
*
Hypertrichosis Hypertrichosis is an abnormal amount of hair growth The growth of human hair occurs everywhere on the body except for the soles of the feet, the inside of the mouth, the lips, the backs of the ears, the palms of the hands, some external genita ...
– the state of having an excess of hair on the head or body *
Hypotrichosis Hair loss, also known as alopecia or baldness, refers to a loss of hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, ...
– the state of having a less than normal amount of hair on the head or body *
Lanugo Lanugo is very thin, soft, usually unpigmented, downy hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chem ...

Lanugo
*
Seta In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

Seta
– hair-like structures in insects *
Trichotillomania Trichotillomania (TTM), also known as hair-pulling disorder or compulsive hair pulling, is a mental disorder A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significan ...

Trichotillomania
– hair pulling


References


Citations


Sources

* * * *


External links

* *
How to measure the diameter of your own hair using a laser pointerInstant insight
outlining the chemistry of hair from the
Royal Society of Chemistry The Royal Society of Chemistry (RSC) is a learned society A learned society (; also known as a learned academy, scholarly society, or academic association) is an organization An organization, or organisation (English in the Commonwea ...
* {{Authority control