Hair is a
protein filament
In biology, a protein filament is a long chain of protein monomers, such as those found in hair, muscle, or in flagella. Protein filaments form together to make the cytoskeleton of the cell. They are often bundled together to provide support, st ...
that grows from
follicles found in the
dermis. Hair is one of the defining characteristics of
mammals.
The
human body, apart from areas of
glabrous
Glabrousness (from the Latin '' glaber'' meaning "bald", "hairless", "shaved", "smooth") is the technical term for a lack of hair, down, setae, trichomes or other such covering. A glabrous surface may be a natural characteristic of all or part of ...
skin, is covered in follicles which produce thick
terminal
Terminal may refer to:
Computing Hardware
* Terminal (electronics), a device for joining electrical circuits together
* Terminal (telecommunication), a device communicating over a line
* Computer terminal, a set of primary input and output dev ...
and fine
vellus hair
Vellus hair is short, thin, light-colored, and barely noticeable hair that develops on most of a human’s body during childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital ...
. 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 areas, the navel, scar tissue, and, apart from eyela ...
, hair types, and
hair care, 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 biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
, notably
alpha-keratin
Alpha-keratin, or α-keratin, is a type of keratin found in vertebrates. This protein is the primary component in hairs, horns, mammalian claws, nails and the epidermis layer of the skin. α-keratin is a fibrous structural protein, meaning it i ...
.
Attitudes towards different forms of hair, such as
hairstyle
A hairstyle, hairdo, haircut or coiffure refers to the 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 groomi ...
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 ...
, 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 usually defined as a social- cultural system of designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that generally relates humanity to supernatural, ...
.
Overview
![506 Hair](https://upload.wikimedia.org/wikipedia/commons/6/68/506_Hair.jpg)
The word "hair" usually refers to two distinct structures:
#the part beneath the skin, called the
hair follicle, or, when pulled from the skin, the bulb or root. This organ is located in the
dermis and maintains
stem cells, which not only re-grow the hair after it falls out, but also are recruited to regrow skin after 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, 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:
Biology
* Cortex (anatomy), the outermost layer of an organ
** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain''
*** Motor cortex, the regions of the cerebral cortex i ...
, which contains the
keratin
Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
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 t ...
, a disorganized and open area at the fiber's center
Description
![Hair follicle of feline - Microscopic view 2](https://upload.wikimedia.org/wikipedia/commons/4/44/Hair_follicle_of_feline_-_Microscopic_view_2.jpg)
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 t ...
,
cortex
Cortex or cortical may refer to:
Biology
* Cortex (anatomy), the outermost layer of an organ
** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain''
*** Motor cortex, the regions of the cerebral cortex i ...
, and
cuticle.
[Hair Structure and Hair Life Cycle](_blank)
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 t ...
, is an open and unstructured region which is not always present.
The highly structural and organized
cortex
Cortex or cortical may refer to:
Biology
* Cortex (anatomy), the outermost layer of an organ
** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain''
*** Motor cortex, the regions of the cerebral cortex i ...
, 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. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...
, which colors the
fiber
Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorpora ...
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. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...
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 or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorpora ...
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
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...
that makes the hair repel water.
The diameter of human hair varies from . There are roughly two million small, tubular glands and
sweat glands 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 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 gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in the greatest nu ...
which lubricates the hair and the
arrector pili muscles, which are responsible for causing hairs to stand up. In humans with little body hair, the effect results in
goose bumps
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 or experiencing strong emotions such as fear, euphoria or sexual arousal.
The ...
.
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 called the
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 German physician, pathologist and anatomist
A ...
) and granular stratum (
Huxley's layer
Huxley's layer is the second layer of the inner root sheath of the hair and consists of one or two layers of horny, flattened, nucleated cells. It lies between Henle's layer and the cuticle. The layer is named after English biologist Thomas Henry ...
), cuticle, cortex and medulla.
Natural color
![Brown hair](https://upload.wikimedia.org/wikipedia/commons/d/df/Brown_hair.jpg)
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 is the dominant pigment in
brown hair
Brown hair, also referred to as brunet (male) or brunette (female), is the second most common human hair color, after black hair. It varies from light brown to a medium dark hair. It is characterized by higher levels of the dark pigment eume ...
and
black hair
Black hair is the darkest and most common of all human hair colors globally, due to larger populations with this dominant trait. It is a dominant genetic trait, and it is found in people of all backgrounds and ethnicities. Black hair contains a ...
, while
pheomelanin
Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the a ...
is dominant in
red hair.
Blond hair
Blond (male) or blonde (female), also referred to as fair hair, is a hair color characterized by low levels of the dark pigment eumelanin. The resultant visible hue depends on various factors, but always has some yellowish color. The color can ...
is the result of having little
pigmentation
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compoun ...
in the hair strand.
Gray hair
Human hair color is the pigmentation of human 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, the hair is lighter. The ...
occurs when melanin production decreases or stops, while
poliosis
Poliosis (also called poliosis circumscripta), is the decrease or absence of melanin (or colour) in head hair, eyebrows, eyelashes or any other hairy area. It is popularly known as white forelock when it affects hair directly above the forehead.
...
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 membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...
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,
catagen
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 areas, the navel, scar tissue, and, apart from eyelas ...
, and
telogen
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 regulates hair growth via a complex interaction between ...
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 that develops on most of a human’s body during childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital ...
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 andr ...
, each with its own type of cellular construction. The different construction gives the hair unique characteristics, serving specific purposes, mainly, warmth and protection.
Texture
![OrangeCat hair](https://upload.wikimedia.org/wikipedia/commons/2/2a/OrangeCat_hair.jpg)
Hair exists in a variety of textures. Three main aspects of hair texture are the curl pattern, volume, and consistency. All mammalian hair is composed of
keratin
Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
, so the make-up of
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 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 terminal and fine ...
has an effect on the curliness of the individual's hair. A very round shaft allows for fewer
disulfide bonds
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...
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
cysteines 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
The Andre Walker Hair Typing System, also known as The Hair Chart is classification system for hair types created in the 1990s by Oprah Winfrey's stylist Andre Walker. It was originally created to market Walker's line of hair care products but has ...
is the most widely used system to classify hair. The system was created by the hairstylist of
Oprah Winfrey,
Andre Walker Andre Walker (born August 19, 1956 in Chicago, Illinois) is a hairstylist from the United States who has won seven Daytime Emmy Awards for Outstanding Achievement in Hairstyling for his work on ''The Oprah Winfrey Show''. He is best known for being ...
. 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 gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in the greatest nu ...
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 that does not align with the surrounding hair, but stands up or curls independently, creating a fuzzy or irregular texture. The three main causes of frizz are genetics, hair damage, and humidity. Frizzy hair can be seen as a positive ...
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 known to have an S-shape. The curl pattern may resemble a lowercase "s", uppercase "S", or sometimes an uppercase "Z" or lowercase "z". Lack of proper care causes less defined curls.
* Type 4 is
kinky hair, 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 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 that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket t ...
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's spotted coat, the b ...
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
![Ursus maritimus Steve Amstrup](https://upload.wikimedia.org/wikipedia/commons/4/4f/Ursus_maritimus_Steve_Amstrup.jpg)
While humans have developed clothing and other means of keeping warm, the hair found on the head serves primarily as a source of heat
insulation 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 injury that occurs when exposed to extreme low temperatures, causing the freezing of the skin or other tissues, commonly affecting the fingers, toes, nose, ears, cheeks and chin areas. Most often, frostbite occurs in the ha ...
and
hypothermia
Hypothermia is defined as a body core temperature below in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe ...
, but the hair on the human body does help to keep the internal temperature regulated. When the body is too cold, the
arrector pili 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. 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 or experiencing strong emotions such as fear, euphoria or sexual arousal.
The f ...
, 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 or experiencing strong emotions such as fear, euphoria or sexual arousal.
The ...
' 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 eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introductio ...
s and
porcupines, 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 close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...
. 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 p ...
, are especially sensitive to the presence of potentially harmful matter.
Eyebrows and eyelashes
![Eyelashes](https://upload.wikimedia.org/wikipedia/commons/8/8d/Eyelashes.jpg)
The
eyebrow
An eyebrow is an area of short hairs above each eye that follows the shape of the lower margin of the brow ridges of some mammals. In humans, eyebrows serve two main functions: first, communication through facial expression, and second, preven ...
s provide moderate protection to the
eyes 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:
* Debris: scattered pieces of waste or remains
* Dust: a gener ...
,
sweat
Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals.
Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. The eccrine sweat glands are distrib ...
and
rain
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water ...
. They also play a key role in non-verbal
communication
Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inqui ...
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 p ...
grows at the edges of the eyelid and protects the eye from dirt. The eyelash is to humans, camels, horses, ostriches etc., what
whiskers
Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarse ...
are to
cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s; they are used to sense when dirt,
dust
Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in ho ...
, or any other potentially harmful object is too close to the eye.
The eye reflexively closes as a result of this
sensation
Sensation (psychology) refers to the processing of the senses by the sensory system.
Sensation or sensations may also refer to:
In arts and entertainment In literature
* Sensation (fiction), a fiction writing mode
* Sensation novel, a Britis ...
.
Evolution
Hair has its origins in the common ancestor of mammals, the
synapsid
Synapsids + (, 'arch') > () "having a fused arch"; synonymous with ''theropsids'' (Greek, "beast-face") are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes reptil ...
s, about 300 million years ago. It is currently unknown at what stage the synapsids acquired mammalian characteristics such as
body hair and
mammary gland
A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in pri ...
s, as the
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
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 or primitive Late Paleozoic synapsids, excluding the therapsids and their descendants. Previously, the term ''mammal-like reptile'' had been used, and pelycosaur was considered an order, but this is ...
, possibly ''
Haptodus
''Haptodus'' is an extinct genus of basal sphenacodont, member of the clade that includes therapsids and hence, mammals. It was at least in length. It lived in present-day France during the Early Permian. It was a medium-sized predator, feeding ...
'' shows the basal synapsid stock bore transverse rows of rectangular
scute
A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...
s, similar to those of a modern
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 ''
Estemmenosuchus'', a
therapsid
Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...
from the
Upper Permian, 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 Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...
(late middle
Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
) ''
Castorocauda'' and several contemporary
haramiyidans, both
near-mammal cynodonts, 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 and System (stratigraphy), stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last ...
Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...
n
coprolites
A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name is d ...
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 is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ' ...
.
Some modern mammals have a special gland in front of each
orbit
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...
used to preen the fur, called the
harderian gland
The Harderian gland is a gland found within the eye's orbit that occurs in tetrapods (reptiles, amphibians, birds and mammals) that possess a nictitating membrane.
The gland can be compound tubular or compound tubuloalveolar, and the fluid it s ...
. Imprints of this structure are found in the skull of the small early mammals like ''
Morganucodon'', but not in their
cynodont ancestors like ''
Thrinaxodon
''Thrinaxodon'' is an extinct genus of cynodonts, most commonly regarded by its species ''T. liorhinus'' which lived in what are now South Africa and Antarctica during the Early Triassic. ''Thrinaxodon'' lived just after the Permian–Triassic m ...
''.
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, a section of the brain that expanded markedly in animals like ''Morganucodon'' and ''
Hadrocodium''. The more advanced therapsids could have had a combination of naked skin,
whiskers, and
scute
A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...
s. A full
pelage
Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket ...
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 and the
opossum.
The high interspecific variability of the size, color, and microstructure of hair often enables the identification of species based on single hair filaments.
![Nacktmull](https://upload.wikimedia.org/wikipedia/commons/0/02/Nacktmull.jpg)
In varying degrees most
mammals 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 animal coverings, such as the arthropod exoskeleton, have different de ...
is found on the
ventral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
portion of the
finger
A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers ( Pentadactyly). Chambers ...
s,
palms,
soles of feet and
lips
The lips are the 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 ...
, 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 vaginal opening in the vulva, situated b ...
and
glans penis
In male human anatomy, the glans penis, commonly referred to as the glans, is the bulbous structure at the distal end of the human penis that is the human male's most sensitive erogenous zone and their primary anatomical source of sexual pl ...
. There are four main types of
mechanoreceptors 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 (specialized nerve ending with adventitious tissue for mechanical sensation) found in mammalian skin. This type of mechanorece ...
,
Meissner's corpuscles,
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
naked mole-rat
The naked mole-rat (''Heterocephalus glaber''), also known as the sand puppy, is a burrowing rodent native to the Horn of Africa and parts of Kenya, notably in Somali regions. It is closely related to the blesmols and is the only species in the ...
(''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 physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compa ...
.
The soft, fine hair found on many nonhuman mammals is typically called fur.
Human hairlessness
Evolutionary variation
Evolutionary biologists suggest that the genus ''
Homo
''Homo'' () is the genus that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' ( modern humans), plus several extinct species classified as either ancestral to or closely relat ...
'' arose in
East Africa 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 physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compa ...
, 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 (10 December 1866, Overschie – 17 June 1930, Amsterdam) was a Dutch anatomist who created the fetalization theory about the human body. It states that when a human being is born, it is still a fetus, as can be seen b ...
made a long list of such traits, and Stephen Jay Gould published a short list in ''Ontogeny and Phylogeny
''Ontogeny and Phylogeny'' is a 1977 book on evolution by Stephen Jay Gould, in which the author explores the relationship between embryonic development (ontogeny) and biological evolution (phylogeny). Unlike his many popular books of essays, it ...
''. In addition, paedomorphic
Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compare ...
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 that has a high quality of life, developed economy and advanced technological infrastruct ...
. For instance, vellus hair
Vellus hair is short, thin, light-colored, and barely noticeable hair that develops on most of a human’s body during childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital ...
is a juvenile characteristic. However, while men develop longer, coarser, thicker, and darker terminal hair
In humans, terminal hair is a variant of hair that is thick and long such as what grows on the scalp, as compared with vellus hair, colloquially known as peach fuzz, growing elsewhere.Marks, James G; Miller, Jeffery (2006)''Lookingbill and M ...
through sexual differentiation
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. Sex determination is often distinct from sex differentiation; sex determination is the designation for the dev ...
, 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 electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
. 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 a human hair texture originating from sub-Saharan Africa. Each strand of this hair type grows in a tiny, angle-like helix shape. The overall effect is such that, contrasted with straight, wavy, or curly hai ...
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 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 a human hair texture originating from sub-Saharan Africa. Each strand of this hair type grows in a tiny, angle-like helix shape. The overall effect is such that, contrasted with straight, wavy, or curly hai ...
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 a human hair texture originating from sub-Saharan Africa. Each strand of this hair type grows in a tiny, angle-like helix shape. The overall effect is such that, contrasted with straight, wavy, or curly hai ...
. 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 of the skin. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area affected. Symptoms begin four to fourteen days after exposure. Multiple ar ...
is a fungal disease
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from t ...
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.
According to the World Health Organization (WHO), "Hygiene refers to conditions and practices that help to maintain health and prevent the spread of diseases." Personal hygiene refer ...
and cosmetology
Cosmetology (from Greek , ''kosmētikos'', "beautifying"; and , '' -logia'') is the study and application of beauty treatment. Branches of specialty include hairstyling, skin care, cosmetics, manicures/ pedicures, non-permanent hair removal such ...
of hair including hair on the scalp
The scalp is the anatomical area bordered by the human face at the front, and by the neck at the sides and back.
Structure
The scalp is usually described as having five layers, which can conveniently be remembered as a mnemonic:
* S: The ski ...
, 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 pubescent or adult males are able to grow beards.
Throughout the course of history, societal at ...
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, and is derived from the Italian ''mustaccio'' ...
), 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 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 ...
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 or any other kind of bladed implement, to slice it down—to the level of the skin or otherwise. Shaving is most commonly practiced by men to remove their facial hair and by women to remove th ...
. Epilation 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 from the root by using a covering of a sticky substance, such as wax, to adhere to body hair, and then removing this covering and pulling out the hair from the follicle. New hair will not grow back in the pr ...
.
Shaving
Shaving
Shaving is the removal of hair, by using a razor or any other kind of bladed implement, to slice it down—to the level of the skin or otherwise. Shaving is most commonly practiced by men to remove their facial hair and by women to remove th ...
is accomplished with bladed instruments, such as razors
A razor is a bladed tool primarily used in the removal of body hair through the act of shaving. Kinds of razors include straight razors, safety razors, disposable razors, and electric razors.
While the razor has been in existence since before ...
. The blade
A blade is the portion of a tool, weapon, or machine with an edge that is designed to puncture, chop, slice or scrape surfaces or materials. Blades are typically made from materials that are harder than those they are to be used on. Histor ...
is brought close to the skin and stroked over the hair in the desired area to cut the terminal hairs and leave the skin feeling smooth. Depending upon the rate of growth, one can begin to feel the hair growing back within hours of shaving. This is especially evident in men who develop a five o'clock shadow after having shaved their faces. This new growth is called stubble. Stubble typically appears to grow back thicker because the shaved hairs are blunted instead of tapered off at the end, although the hair never actually grows back thicker.
Waxing
Waxing
Waxing is the process of hair removal from the root by using a covering of a sticky substance, such as wax, to adhere to body hair, and then removing this covering and pulling out the hair from the follicle. New hair will not grow back in the pr ...
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 through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fi ...
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 from the root by using a covering of a sticky substance, such as wax, to adhere to body hair, and then removing this covering and pulling out the hair from the follicle. New hair will not grow back in the pr ...
or shaving
Shaving is the removal of hair, by using a razor or any other kind of bladed implement, to slice it down—to the level of the skin or otherwise. Shaving is most commonly practiced by men to remove their facial hair and by women to remove th ...
. 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 or clippers
The Los Angeles Clippers are an American professional basketball team based in Los Angeles. The Clippers compete in the National Basketball Association (NBA) as a member of the Pacific Division in the league's Western Conference. The Clipper ...
. 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' ...
s. Global imports of hair in 2010 was worth $US 1.24 billion.
Social role
Hair has great social significance for human beings. It can grow on most external areas of the human body, except on the palms of the hands 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 shaved. These include the face
The face is the front of an animal's head that features the eyes, nose and mouth, and through which animals express many of their emotions. The face is crucial for human identity, and damage such as scarring or developmental deformities may aff ...
, ear
An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...
s, head, eyebrows, leg
A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element ca ...
s, and armpit
The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and the thoracic cage, bounded superior ...
s, as well as the pubic region. 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 in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a s ...
.
The world's longest documented hair belongs to Xie Qiuping
Xie Qiuping (, born c. 1960) is a Chinese woman who holds the record for world's longest hair. On 8 May 2004, her hair was measured to be 5.627 meters (18 ft 5.54 in). She began growing her hair to its current length in 1973 at the age of 13. ...
(in 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 that studies the evolutionary processes ( natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life ...
). Hair color and texture can be a sign of ethnic ancestry. Facial hair is a sign of puberty
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a bo ...
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 cosmetic: to cover gray or white hair, to change to a color regarded as more fashionable or desirable, or to restore the original hair color ...
(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 (or colour) in head hair, eyebrows, eyelashes or any other hairy area. It is popularly known as white forelock when it affects hair directly above the forehead.
...
characteristic of the person since childhood). Male pattern baldness 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 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 groomi ...
may be an indicator of group membership. During the English Civil War
The English Civil War (1642–1651) was a series of civil wars and political machinations between Parliamentarians (" Roundheads") and Royalists led by Charles I ("Cavaliers"), mainly over the manner of England's governance and issues of re ...
, the followers of Oliver Cromwell
Oliver Cromwell (25 April 15993 September 1658) was an English politician and military officer who is widely regarded as one of the most important statesmen in English history. He came to prominence during the 1639 to 1651 Wars of the Three K ...
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, is a short to medium length haircut, in which the hair is typically cut straight around the head at approximately jaw level, but no longer than shoulder-length, often with fringe or bangs at the front. The standa ...
was popular among the flapper
Flappers were a subculture of young Western women in the 1920s who wore short skirts (knee height was considered short during that period), bobbed their hair, listened to jazz, and flaunted their disdain for what was then considered accepta ...
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 usually refers to a "male" pattern of hair growth in a female that ...
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 hippies, metalheads, and Indian sadhus
''Sadhu'' ( sa, साधु, IAST: ' (male), ''sādhvī'' or ''sādhvīne'' (female)), also spelled ''saddhu'', is a religious ascetic, mendicant or any holy person in Hinduism, Buddhism, and Jainism who has renounced the worldly life. The ...
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 cultures ...
, as well many older indie kids
The 21st-century hipster is a subculture (sometimes called hipsterism). Fashion is one of the major markers of hipster identity. Members of the subculture typically do not self-identify as hipsters, and the word ''hipster'' is often used as a pej ...
. Many punks
Punk or punks may refer to:
Genres, subculture, and related aspects
* Punk rock, a music genre originating in the 1970s associated with various subgenres
* Punk subculture, a subculture associated with punk rock, or aspects of the subculture ...
wear a hairstyle known as a mohawk Mohawk 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 ...
or other spiked and dyed hairstyles; skinhead
A skinhead is a member of a subculture which originated among working class youths in London, England, in the 1960s and soon spread to other parts of the United Kingdom, with a second working class skinhead movement emerging worldwide in th ...
s have short-cropped or completely shaved heads. Long stylized bangs were very common for emo
Emo is a rock music genre characterized by emotional, often confessional lyrics. It emerged as a style of and hardcore punk from the Washington D.C. hardcore punk scene, where it was known as emotional hardcore or emocore and pioneered b ...
s, scene kids and younger indie kids
The 21st-century hipster is a subculture (sometimes called hipsterism). Fashion is one of the major markers of hipster identity. Members of the subculture typically do not self-identify as hipsters, and the word ''hipster'' is often used as a pej ...
in the 2000s and early 2010s, among people of both gender
Gender is the range of characteristics pertaining to femininity and masculinity and differentiating between them. Depending on the context, this may include sex-based social structures (i.e. gender roles) and gender identity. Most cultures ...
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 wartime or of terrorism suspects". Thus, while it can simpl ...
s, and head-shaving has been used as 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. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...
haircuts, while Western monks are known for the tonsure
Tonsure () is the practice of cutting or shaving some or all of the hair on the scalp as a sign of religious devotion or humility. The term originates from the Latin word ' (meaning "clipping" or "shearing") and referred to a specific practice i ...
. 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 known as locs or dreads, are rope-like strands of hair formed by locking or braiding hair.
Origins
Some of the earliest depictions of dreadlocks date back as far as 1600–1500 BCE in the Minoan Civilization, one of Europe ...
of the Rastafari movement
Rastafari, sometimes called Rastafarianism, is a religion that developed in Jamaica during the 1930s. It is classified as both a new religious movement and a social movement by scholars of religion. There is no central authority in control of ...
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
The afro is a hair type created by natural growth of kinky hair, or specifically styled with chemical curling products by individuals with naturally curly or straight hair.Garland, Phyl"Is The Afro On Its Way Out?" ''Ebony'', February 1973. ...
. This hairstyle was once worn among African American
African Americans (also referred to as Black Americans and Afro-Americans) are an ethnic group consisting of Americans with partial or total ancestry from sub-Saharan Africa. The term "African American" generally denotes descendants of ens ...
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 worldview that is centered on Western civilization or a biased view that favors it over non-Western civilizations. The exact scope of Eurocentrism varies from the entire Western worl ...
) 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 drug culture road drama film written by Peter Fonda, Dennis Hopper, and Terry Southern, produced by Fonda, and directed by Hopper. Fonda and Hopper play two bikers who travel through the American So ...
'' (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 whose values and norms of behavior differ substantially from those of mainstream society, sometimes diametrically opposed to mainstream cultural mores.Eric Donald Hirsch. ''The Dictionary of Cultural Literacy''. Hou ...
. 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 and with over 217 million people, Brazil is the world's fifth-largest country by area ...
in the mid-2000s, allegedly because of his fauxhawk
The mohawk (also referred to as a Mohican) is a hairstyle in which, in the most common variety, both sides of the head are shaven, leaving a strip of noticeably longer hair in the center. It is today worn as an emblem of non-conformity.
The m ...
haircut, sparked national debate and legal action resulting in compensation.
Religious practices
Women's hair may be hidden using headscarves, a common part of the '' hijab'' in Islam and a symbol of modesty required for certain religious rituals in Eastern Orthodoxy
Eastern Orthodoxy, also known as Eastern Orthodox Christianity, is one of the three main branches of Chalcedonian Christianity, alongside Catholicism and Protestantism.
Like the Pentarchy of the first millennium, the mainstream (or "canonical") ...
. Russian Orthodox Church
, native_name_lang = ru
, image = Moscow July 2011-7a.jpg
, imagewidth =
, alt =
, caption = Cathedral of Christ the Saviour in Moscow, Russia
, abbreviation = ROC
, type ...
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 and theologically conservative branches of contemporary Judaism. Theologically, it is chiefly defined by regarding the Torah, both Written and Oral, as revealed by God to Moses ...
also commands the use of scarves and other head coverings for married women for modesty reasons. Certain Hindu
Hindus (; ) are people who religiously adhere to Hinduism. Jeffery D. Long (2007), A Vision for Hinduism, IB Tauris, , pages 35–37 Historically, the term has also been used as a geographical, cultural, and later religious identifier for ...
sects also wear head scarves for religious reasons. Sikhs 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 دولبند, ''dulband''; via Middle French ''turbant'') is a type of headwear based on cloth winding. Featuring many variations, it is worn as customary headwear by people of various cultures. Communities with promin ...
. Multiple religions, both ancient and contemporary, require or advise one to allow their hair to become dreadlocks
Dreadlocks, also known as locs or dreads, are rope-like strands of hair formed by locking or braiding hair.
Origins
Some of the earliest depictions of dreadlocks date back as far as 1600–1500 BCE in the Minoan Civilization, one of Europe ...
, 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 madhab
A ( ar, مذهب ', , "way to act". pl. مَذَاهِب , ) is a school of thought within '' fiqh'' (Islamic jurisprudence).
The major Sunni Mathhab are Hanafi, Maliki, Shafi'i and Hanbali.
They emerged in the ninth and tenth centurie ...
s, the donning of a kufi
A kufi or kufi cap is a brimless, short, and rounded cap worn by men in many populations in North Africa, East Africa, West Africa, and South Asia. It is also worn by men throughout the African diaspora. It is also commonly called a "topi" or ...
or topi
''Damaliscus lunatus jimela'' is a subspecies of topi, and is usually just called a topi. It is a highly social and fast type of antelope found in the savannas, semi-deserts, and floodplains of sub-Saharan Africa.
Names
The word ''tope'' o ...
is a form of sunnah.[The War Within Our Hearts – Page 65 Sa'ad Quadri – 2013]
In Arabic poetry
Since ancient times, women's long, thick, wavy hair has featured prominently in Arabic poetry. Pre-Islamic poets used only limited imagery to describe women's hair. For example, al-A'sha
Al-A'sha ( ar, ٱلْأَعْشَىٰ) or Maymun Ibn Qays Al-A'sha (d.c. 570– 625) was an Arabic Jahiliyyah poet from Najd, Arabia.
He traveled through Mesopotamia, Syria, Arabia and Ethiopia. He was nicknamed Al-A'sha which means "weak-sig ...
wrote a verse comparing a lover's hair to "a garden whose grapes dangle down upon me", but Bashar ibn Burd
Bashār ibn Burd ( ar, بشار بن برد; 714–783), nicknamed al-Mura'ath, meaning "the wattled", was a Persian poet of the late Umayyad and early Abbasid periods who wrote in Arabic. Bashar was of Persian ethnicity; his grandfather was take ...
considered this unusual. One comparison used by early poets, such as Imru al-Qays, was to bunches of date
Date or dates may refer to:
*Date (fruit), the fruit of the date palm (''Phoenix dactylifera'')
Social activity
*Dating, a form of courtship involving social activity, with the aim of assessing a potential partner
** Group dating
*Play date, a ...
s. In Abbasid
The Abbasid Caliphate ( or ; ar, الْخِلَافَةُ الْعَبَّاسِيَّة, ') was the third caliphate to succeed the Islamic prophet Muhammad. It was founded by a dynasty descended from Muhammad's uncle, Abbas ibn Abdul-Muttalib ...
times, however, the imagery for hair expanded significantly - particularly for the then-fashionable "love-locks" (''sudgh'') framing the temple
A temple (from the Latin ) is a building reserved for spiritual rituals and activities such as prayer and sacrifice. Religions which erect temples include Christianity (whose temples are typically called churches), Hinduism (whose temples ...
s, which came into style at the court of the caliph al-Amin
Abu Musa Muhammad ibn Harun al-Rashid ( ar, أبو موسى محمد بن هارون الرشيد, Abū Mūsā Muḥammad ibn Hārūn al-Rashīd; April 787 – 24/25 September 813), better known by his laqab of Al-Amin ( ar, الأمين, al-Amī ...
. Hair curls were compared to hooks and chains, letters (such as '' fa'', '' waw'', '' lam'', and ''nun
A nun is a woman who vows to dedicate her life to religious service, typically living under vows of poverty, chastity, and obedience in the enclosure of a monastery or convent.''The Oxford English Dictionary'', vol. X, page 599. The term is o ...
''), scorpion
Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always en ...
s, annelids, and polo sticks. An example was the poet Ibn al-Mu'tazz
Abdallah ibn al-Mu'tazz ( ar, عبد الله بن المعتز, ʿAbd Allāh ibn al-Muʿtazz; 861 – 17 December 908) was the son of the caliph al-Mu'tazz and a political figure, but is better known as a leading Arabic poet and the author o ...
, who compared a lock of hair and a birthmark
A birthmark is a congenital, benign irregularity on the skin which is present at birth or appears shortly after birth—usually in the first month. They can occur anywhere on the skin. Birthmarks are caused by overgrowth of blood vessels, melanocy ...
to a polo stick driving a ball.
See also
* Body hair
* Chaetophobia – the fear of hair
* Hair analysis (alternative medicine)
In mainstream scientific usage, hair analysis is the chemical analysis of a hair sample. The use of hair analysis in alternative medicine as a method of investigation to assist alternative diagnosis is controversial and its use in this manner h ...
* Hypertrichosis
Hypertrichosis is an abnormal amount of hair growth over the body. The two distinct types of hypertrichosis are generalized hypertrichosis, which occurs over the entire body, and localized hypertrichosis, which is restricted to a certain area. ...
– 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 from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarri ...
– the state of having a less than normal amount of hair on the head or body
* Lanugo
* Seta
In biology, setae (singular seta ; from the Latin word for " bristle") are any of a number of different bristle- or hair-like structures on living organisms.
Animal setae
Protostomes
Annelid setae are stiff bristles present on the body. ...
– hair-like structures in insects
* Bristle sensilla
Bristle sensilla (sometimes also called tactile hairs) are a class of mechanoreceptors found in insects and other arthropods that respond to mechanical stimuli generated by the external world. As a result, they are considered exteroceptors. Bris ...
– tactile hairs in insects
* Trichotillomania
Trichotillomania (TTM), also known as hair-pulling disorder or compulsive hair pulling, is a mental disorder characterized by a long-term urge that results in the pulling out of one's own hair. A brief positive feeling may occur as hair is remov ...
– hair pulling
References
Citations
Sources
*
*
*
*
External links
*
*
How to measure the diameter of your own hair using a laser pointer
Instant insight
outlining the chemistry of hair from the Royal Society of Chemistry
The Royal Society of Chemistry (RSC) is a learned society (professional association) in the United Kingdom with the goal of "advancing the chemical sciences". It was formed in 1980 from the amalgamation of the Chemical Society, the Royal Instit ...
*
{{Authority control