Human skin color
Encyclopedia
Human skin color is primarily due to the presence of melanin
in the skin. Skin color ranges from almost black to white with a pinkish tinge due to blood vessels underneath. Variation in natural skin color is mainly due to genetics
, although the evolutionary causes are not completely certain. According to scientific studies, natural human skin color diversity is highest in Sub-Saharan African populations, with skin reflectance values ranging from 19 to 46 (med.
31) compared with Europe
an and East Asian populations which have skin reflectance values of 62 to 69 and 50 to 59 respectively. The term "range" is loosely defined in this case, as African albinos have obviously not been taken into consideration when calculating the "range".
The natural skin color can be darkened as a result of tanning
due to exposure to sunlight. The leading explanation is that skin color adapts to sunlight intensities which produce vitamin D
or ultraviolet
light damage to folic acid
. Other hypotheses include protection from ambient temperature, infections, skin cancer
or frostbite
, an alteration in food, and sexual selection
.
The social significance of differences in skin color has varied across cultures and over time, as demonstrated with regard to social status
and racism
.
s in a process called melanogenesis. Melanin is triggered by an enzyme
called tyrosinase
, which creates the color of skin, eyes, and hair shades. Melanocytes produce two types of melanin: pheomelanin (red) and eumelanin (very dark brown). Both the amount and type of melanin produced is controlled by a number of gene
s which operate under incomplete dominance. One copy of each of the various genes is inherited from each parent. Each gene can come in several allele
s, resulting in the great variety of human skin tones.
Melanin controls the amount of ultraviolet
(UV) radiation from the sun that penetrates the skin by absorption. While UV radiation can assist in the production of vitamin D, excessive exposure to UV can damage health.
(KITLG) gene is involved in the permanent survival, proliferation and migration of melanocytes. A mutation of this gene, A326G (rs642742) has been positively associated with variations of skin color in African-Americans of mixed West African and European descent and is estimated to account for 15–20% of the melanin difference between African and non-African populations. The A326G allele occurs in over 80% of European and Asian samples, compared with less than 10% in African samples.
Agouti signalling peptide
(ASIP) acts as an inverse agonist
, binding in place of alpha-MSH
and thus inhibiting eumelanin production. Studies have found alleles in the vicinity of ASIP are associated with skin color in humans – rs2424984 has been identified as one of three indicators of skin tone in a forensics analysis of human phenotypes and has a frequency of roughly 80% in Europeans, 75% in Asians and 20–25% in Africans. A 2-SNP haplotype
(rs4911414 and rs1015362) has also been linked with skin color variation within European populations and has a similar frequency distribution.
Solute carrier family 24 member 5
(SLC24A5) regulates calcium in melanocytes and is important in the process of melanogenesis. The Thr111Ala allele (rs1426654) has been shown to be a major factor in the light skin tone of Europeans in a number of studies. It is virtually non-existent in Asian and African populations and is found in about 99.9% of Europeans. It is believed to represent some 25–40% of the difference in skin tone between Europeans and Africans, and appears to have arisen as recently as within the last 10,000 years.
Solute carrier family 45 member 2
(SLC45A2 or MATP) aids in the transport and processing of tyrosine
, a precursor to melanin. It has also been shown to be a major factor in the skin color of modern Europeans through its Phe374Leu (rs16891982) variation. Like SLC24A5 it is ubiquitous in European populations but extremely rare elsewhere.
The TYR
gene encodes the enzyme tyrosinase which is involved in the production of melanin from tyrosine. It has an allele, Ser192Tyr (rs1042602), found solely in 40–50% of Europeans and linked to light-colored skin in studies of mixed-race populations.
Oculocutaneous albinism II
(OCA2) assists in the regulation of pH
in melanocytes. The His615Arg (rs1800414) allele has been shown to account for about 8% of the skin tone difference between African and East Asian populations. It is found in 85% of East Asian samples and is non-existent in European and African samples.
A number of studies have found a genes linked to human skin pigmentation that have alleles with statistically significant frequencies in Asian populations. While not linked to measurements of skin tone variation directly, dopachrome tautomerase
(DCT or TYRP2 rs2031526), melanocortin 1 receptor
(MC1R) Arg163Gln (rs885479) and attractin
(ATRN) have been indicated as potential contributors to the evolution of light skin in East Asian populations.
Mutations in genes can cause also affect skin color through oculocutaneous albinism
(OCA) – a lack of pigment in the eyes, skin and sometimes hair that occurs occasionally in a very small fraction of the population. The four known types of OCA are caused by mutations of the TYR, OCA2, TYRP1
and SLC45A2 genes.
The gene MC1R
is primarily responsible for determining whether pheomelanin and eumelanin is produced in humans. Mutations of this very polymorphic
gene, such as Arg151Sys (rs1805007), Arg160Trp (rs1805008), Asp294Sys (rs1805009), Val60Leu (rs1805005) and Val92Met (rs2228479) have been shown to cause red hair
and pale skin that does not tan in a small percentage of the human population. Although these alleles have differing frequencies across African, European and Asian populations, there is no evidence of positive selection for them and they do not appear to be associated with the evolution of lighter skin in Eurasian populations.
and protect from folate depletion due to the increased exposure to sunlight. By 1.2 million years ago, around the time of homo ergaster
and homo erectus
, the ancestors of all people living today had exactly the same receptor protein as modern Africans. Evolutionary pressure meant that any gene variations that resulted in lighter skin were unable to survive under the intense African sun, and human skin remained dark for the next 1.1 million years.
Approximately 70,000–100,000 years ago modern humans began to migrate away from the tropics to the north where they were exposed to less intense sunlight, possibly in part due to the need for greater use of clothing to protect against the colder climate. Under these conditions there was less photodestruction of folate and so the evolutionary pressure stopping lighter-skinned gene variants from surviving was reduced. In addition, lighter skin is able to generate more vitamin D
(cholecalciferol) than darker skin so it would have represented a health benefit in reduced sunlight if there were limited sources of vitamin D. Hence the leading hypothesis for the evolution of human skin color proposes that:-
The genetic mutations leading to light skin, though different among East Asians and Europeans, suggest the two groups experienced a similar selective pressure due to settlement in northern latitudes.
There is a long-standing hypothesis that the selection for lighter skin due to higher vitamin D absorption occurred soon after the Out of Africa
migration sometime before 40,000 years ago. A number of researchers disagree with this and suggest that the northern latitudes permitted enough synthesis of vitamin D combined with food sources from hunting to keep populations healthy, and only when agriculture was adopted was there a need for lighter skin to maximize the synthesis of vitamin D. The theory suggests that the reduction of game meat, fish, and some plants from the diet resulted in skin turning clear many thousands of years after settlement in Europe and Asia. This theory is supported by a study into the SLC24A5
gene which found that the allelle associated with light skin in Europe may have originated as recently as 6,000–10,000 years ago which is in line with the earliest evidence of farming.
One of the most recently proposed drivers of the evolution of skin pigmentation in humans is based on research that shows a superior barrier function in darkly pigmented skin . Most protective functions of the skin, including the permeability barrier and the antimicrobial barrier, reside in the stratum corneum (SC). It seems logical to surmise that the SC has undergone the most genetic change since the loss of human body hair. Natural selection would have favored mutations that protect this essential barrier; one such protective adaptation is the pigmentation of interfollicular epidermis, because it improves barrier function as compared to non-pigmented skin. In lush rainforests, however, where UV-B radiation and xeric stress were not in excess, light pigmentation would not have been nearly as detrimental. This explains the side-by-side residence of lightly pigmented and darkly pigmented peoples.
Increased melanin production, also known as hyperpigmentation
, can be:
Aside from sun exposure and hormones, hyperpigmentation can be caused by skin damage, such as remnants of blemishes, wounds or rashes. This is especially true for those with darker skin tones.
The most typical cause of darkened areas of skin, brown spots or areas of discoloration is unprotected sun exposure. Once incorrectly referred to as liver spots
, these pigment problems are not connected with the liver.
On lighter to medium skin tones, solar lentigenes emerge as small- to medium-sized brown patches of freckling that can grow and accumulate over time on areas of the body that receive the most unprotected sun exposure, such as the back of the hands, forearms, chest, and face. For those with darker skin colors, these discolorations can appear as patches or areas of ashen-gray skin.
in the skin protects the body by absorbing solar radiation. In general, the more melanin there is in the skin the more solar radiation can be absorbed. Excessive solar radiation causes direct
and indirect DNA damage
to the skin and the body naturally combats and seeks to repair the damage and protect the skin by creating and releasing further melanin into the skin's cells. With the production of the melanin, the skin color darkens, but can also cause sunburn. The tanning process can also be created by artificial UV radiation.
There are two different mechanisms involved. Firstly, the UVA-radiation creates oxidative stress, which in turn oxidizes existing melanin and leads to rapid darkening of the melanin. Secondly, there is an increase in production of melanin (melanogenesis). Melanogenesis leads to delayed tanning and first becomes visible about 72 hours after exposure. The tan that is created by an increased melanogenesis lasts much longer than the one that is caused by oxidation of existing melanin.
A person's natural skin color has an impact on their reaction to exposure to the sun. The tone of human skin can vary from a dark brown to a nearly colorless pigmentation, which may appear reddish due to the blood in the skin. Europeans generally have lighter skin, hair, and eyes than any other group, although this is not always the case. Africans generally have darker skin, hair, and eyes, although this too is not universal. For practical purposes, such as exposure time for sun tanning
, six skin types are distinguished following Fitzpatrick (1975), listed in order of decreasing lightness:
Dark skin with large concentrations of melanin protects against exposure to ultraviolet
light and skin cancer
s; light-skinned people have about a tenfold greater risk of dying from skin cancer, compared with dark-skinned persons, under equal sunlight
exposure. Furthermore, UV-A
rays from sunlight are believed to interact with folic acid
in ways which may damage health.
In a number of traditional societies the sun was avoided as much as possible, especially around noon when the ultraviolet radiation in sunlight is at its most intense. Midday was a time when people stayed in the shade and had the main meal followed by a nap.
While dark skin offers better protection from intense ultraviolet light, it may result in low vitamin D levels and has led to concern that darker skinned people living at relatively high latitude, such as African Americans, may have inadequate vitamin D levels. Research shows that dark-skinned people living in Western societies have lower vitamin D levels. The explanation for low vitamin D levels in dark-skinned people is thought to be that melanin
in the skin hinders vitamin D synthesis. However, recent studies have found novel evidence that low vitamin D levels among people of African ancestry may be due to other reasons, such as that black women have an increase in serum parathyroid hormone
– implicated in adverse cardiovascular outcomes – at a lower vitamin D level than white women. In a large scale association study of the genetic determinants of vitamin D insufficiency in Caucasians no links to pigmentation were found.
Because skin color has been under strong selective pressure, similar skin colors can result from convergent adaptation rather than from genetic relatedness, populations with similar pigmentation may be genetically no more similar than other widely separated groups. Furthermore, in some parts of the world in which people from different regions have mixed extensively, the connection between skin color and ancestry has been substantially weakened. In Brazil, for example, skin color is not closely associated with the percentage of recent African ancestors a person has, as estimated from an analysis of genetic variants differing in frequency among continent groups.
Considerable speculation has surrounded the possible adaptive value of other physical features characteristic of groups, such as the constellation of facial features observed in many eastern and northeastern Asians. However, any given physical characteristic generally is found in multiple groups, and demonstrating that environmental selective pressures shaped specific physical features will be difficult, since such features may have resulted from sexual selection for individuals with certain appearances or from genetic drift.
in ancient Egypt
, Greece
or Rome
. Relations between the major power and the subordinate state was viewed as more significant in a person's status than was their skin color.
The preferred skin tone varies by culture and has varied over time. A number of indigenous African groups, such as the Maasai, associated pale skin with being cursed or caused by evil spirits associated with witchcraft. They would abandon their children born with conditions such as albinism
and showed a sexual preference for darker skin.
Many cultures have historically favored lighter skin for women. In Europe, before the Industrial Revolution
, pale skin was preferred and was a sign of high social status. The poorer classes worked outdoors and got darker skin from exposure to the sun, while the upper class stayed indoors and had light skin. Light skin became associated with wealth and high position. Women even went as far as to put lead-based cosmetics on their skin to artificially whiten their skin tone. However, when not strictly monitored these cosmetics caused lead poisoning
. Achieving a light-skinned appearance was brought about in many other ways, including the use of arsenic
to whiten skin, and powders. Other methods included wearing full-length clothes when outdoors, including gloves and parasols.
Colonization and slavery by European countries inspired racism
, led by the belief that people with dark skin were uncivilized and were to be considered inferior and subordinate to the "white races", which has continued to be perpetuated in modern times. During slavery
, lighter-skinned African Americans were perceived as more intelligent, cooperative, and beautiful. They were more likely to work as house slaves and were also given preferential treatment by plantation owners and the overseers. For example, they had a chance to get an education while darker African Americans worked in the fields and did not get an education. The preference for fair-skin remained prominent until the end of the Victorian era
, but the racial stereotypes about worth and beauty were still persistent in the last half of the 20th century. African American journalist Jill Nelson
wrote that "to be both prettiest and black was impossible" and elaborated:
In some countries, there continues to be a preference for fair or lighter skin, even in Latin American countries where whites are a minority. In Mexico, light skin is associated with power, as well as attractiveness. A dark-skinned person is more likely to be discriminated against in Brazil. Many Latin American actors and actresses have European features—blond hair, blue eyes, and pale skin. A light-skinned person is considered to be more privileged and have a higher social status; a person with light skin is considered more beautiful and it means that the person has more wealth. Skin color is such an obsession in some countries that specific words describe distinct skin tones from "hincha", Puerto Rican slang for "glass of milk" to "morena", literally "brown".
Skin whitening
products have remained prominent over time, often due to historical beliefs and perceptions about fair skin. In South and East Asian countries, light skin has traditionally been seen as more attractive and a preference for lighter skin remains prevalent. In ancient China and Japan, for example, pale skin can be traced back to ancient drawings depicting women and goddesses with fair skin tones. In ancient China, Japan, and Southeast Asia, pale skin was seen as a sign of wealth. Thus, skin whitening cosmetic products are popular in East Asia. 4 out of 10 women surveyed in Hong Kong
, Malaysia, the Philippines
and South Korea
used a skin-whitening cream, and more than 60 companies globally compete for Asia's estimated $18 billion market. Changes in regulations in the cosmetic industry led to skin care companies introducing harm free skin lighteners. This also occurs in South Asian countries, and in India
, pale skin is considered more attractive and skin whitening is common. Most actors and actresses have light skin. In Japan
, the geisha
was well known for their white painted faces, and the appeal of the , or "beautiful white", ideal leads many Japanese women to avoid any form of tanning. There are exceptions to this, with Japanese fashion trends such as ganguro
emphasizing almost black skin, while, in India, dark skin is sometimes associated with a lower class status and some people resort to skin bleaching to achieve a skin color they consider more socially desirable. Skin whitening products sales across the world grew from $40 to $43 billion in 2008. Skin whitening is also not uncommon in Africa
, and several research projects have suggested a general preference for lighter skin in the African-American community. In contrast, one study on men of the Bikosso tribe in Cameroon found no preference for attractiveness of females based on lighter skin color, bringing into question the universality of earlier studies that had exclusively focused on skin color preferences among non-African populations.
It has been found that, on average, women of a given ancestry have a lighter skin tone than men of the same ancestry and that there is a sexual preference for paleness in women and darkness in men in many cultures throughout the world. In his foreword to Peter Frost's
2005 Fair Women, Dark Men, University of Washington
sociologist Pierre L. van den Berghe stated, "Although virtually all cultures express a marked preference for fair female skin, even those with little or no exposure to European imperialism, and even those whose members are heavily pigmented, many are indifferent to male pigmentation or even prefer men to be darker." He elaborated that popular media in the Western world has repeatedly associated blacks with "advantageous stereotypes," as much as negative ones, such as "myths that praise their athletic aptitudes amongst many other things, and often depict them as males of superior genetic inheritance".
Significant exceptions to a preference for lighter skin started to appear in Western culture mid-20th century. Though sun-tanned skin used to be associated with the sun-exposed manual labor of the lower-class, the associations became dramatically reversed during this time – a change usually credited to the trendsetting French woman Coco Chanel
making tanned skin seem fashionable, healthy, and luxurious. Today, though a preference for lighter skin remains prevalent in the United States, many within the country regard tanned skin as both more attractive and healthier than pale skin. Western mass media and popular culture continued to reinforce negative stereotypes about dark skin, but pale skin has become associated with indoor office work while tanned skin has become associated with increased leisure time, sportiness and good health that comes with wealth and higher social status. Studies indicating that the degree of tanning is directly related to how attractive a young woman is have also emerged. The election of a dark-skinned United States President and the financial success of many African-American singers and actors has challenged a number of stereotypes associated with darker skin tones. There has also been an increase in the perceived attractiveness of dark-skinned women.
Other:
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...
in the skin. Skin color ranges from almost black to white with a pinkish tinge due to blood vessels underneath. Variation in natural skin color is mainly due to genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
, although the evolutionary causes are not completely certain. According to scientific studies, natural human skin color diversity is highest in Sub-Saharan African populations, with skin reflectance values ranging from 19 to 46 (med.
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
31) compared with Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
an and East Asian populations which have skin reflectance values of 62 to 69 and 50 to 59 respectively. The term "range" is loosely defined in this case, as African albinos have obviously not been taken into consideration when calculating the "range".
The natural skin color can be darkened as a result of tanning
Sun tanning
Sun tanning or simply tanning is the process whereby skin color is darkened or tanned. The process is most often a result of exposure to ultraviolet radiation from the sun or from artificial sources, such as a tanning bed, but can also be a result of windburn or reflected light...
due to exposure to sunlight. The leading explanation is that skin color adapts to sunlight intensities which produce vitamin D
Vitamin D
Vitamin D is a group of fat-soluble secosteroids. In humans, vitamin D is unique both because it functions as a prohormone and because the body can synthesize it when sun exposure is adequate ....
or ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light damage to folic acid
Folic acid
Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...
. Other hypotheses include protection from ambient temperature, infections, skin cancer
Skin cancer
Skin neoplasms are skin growths with differing causes and varying degrees of malignancy. The three most common malignant skin cancers are basal cell cancer, squamous cell cancer, and melanoma, each of which is named after the type of skin cell from which it arises...
or frostbite
Frostbite
Frostbite is the medical condition where localized damage is caused to skin and other tissues due to extreme cold. Frostbite is most likely to happen in body parts farthest from the heart and those with large exposed areas...
, an alteration in food, and sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...
.
The social significance of differences in skin color has varied across cultures and over time, as demonstrated with regard to social status
Social status
In sociology or anthropology, social status is the honor or prestige attached to one's position in society . It may also refer to a rank or position that one holds in a group, for example son or daughter, playmate, pupil, etc....
and racism
Racism
Racism is the belief that inherent different traits in human racial groups justify discrimination. In the modern English language, the term "racism" is used predominantly as a pejorative epithet. It is applied especially to the practice or advocacy of racial discrimination of a pernicious nature...
.
Melanin and genes
Melanin is produced by cells called melanocyteMelanocyte
-External links: - "Eye: fovea, RPE" - "Integument: pigmented skin"...
s in a process called melanogenesis. Melanin is triggered by an enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
called tyrosinase
Tyrosinase
Tyrosinase also known as monophenol monooxygenase is an enzyme that catalyses the oxidation of phenols and is widespread in plants and animals...
, which creates the color of skin, eyes, and hair shades. Melanocytes produce two types of melanin: pheomelanin (red) and eumelanin (very dark brown). Both the amount and type of melanin produced is controlled by a number of gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s which operate under incomplete dominance. One copy of each of the various genes is inherited from each parent. Each gene can come in several allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
s, resulting in the great variety of human skin tones.
Melanin controls the amount of ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
(UV) radiation from the sun that penetrates the skin by absorption. While UV radiation can assist in the production of vitamin D, excessive exposure to UV can damage health.
Genetics of skin color variation
The KIT ligandStem cell factor
Stem Cell Factor is a cytokine that binds to the c-Kit receptor . SCF can exist both as a transmembrane protein and a soluble protein...
(KITLG) gene is involved in the permanent survival, proliferation and migration of melanocytes. A mutation of this gene, A326G (rs642742) has been positively associated with variations of skin color in African-Americans of mixed West African and European descent and is estimated to account for 15–20% of the melanin difference between African and non-African populations. The A326G allele occurs in over 80% of European and Asian samples, compared with less than 10% in African samples.
Agouti signalling peptide
Agouti signalling peptide
Agouti signalling peptide, a product of the Agouti gene, is a peptide consisting of 131 amino acids. Its discovery was published in 1994 in the scientific journal Nature where its functional properties were described...
(ASIP) acts as an inverse agonist
Inverse agonist
In the field of pharmacology, an inverse agonist is an agent that binds to the same receptor as an agonist but induces a pharmacological response opposite to that agonist....
, binding in place of alpha-MSH
Melanocyte-stimulating hormone
The melanocyte-stimulating hormones are a class of peptide hormones that are produced by cells in the intermediate lobe of the pituitary gland...
and thus inhibiting eumelanin production. Studies have found alleles in the vicinity of ASIP are associated with skin color in humans – rs2424984 has been identified as one of three indicators of skin tone in a forensics analysis of human phenotypes and has a frequency of roughly 80% in Europeans, 75% in Asians and 20–25% in Africans. A 2-SNP haplotype
Haplotype
A haplotype in genetics is a combination of alleles at adjacent locations on the chromosome that are transmitted together...
(rs4911414 and rs1015362) has also been linked with skin color variation within European populations and has a similar frequency distribution.
Solute carrier family 24 member 5
SLC24A5
Sodium/potassium/calcium exchanger 5 also known as solute carrier family 24 member 5 is a protein that in humans is encoded by the SLC24A5 gene that has a major influence on natural skin colour variation. The NCKX5 protein is a member of the potassium-dependent sodium/calcium exchanger family...
(SLC24A5) regulates calcium in melanocytes and is important in the process of melanogenesis. The Thr111Ala allele (rs1426654) has been shown to be a major factor in the light skin tone of Europeans in a number of studies. It is virtually non-existent in Asian and African populations and is found in about 99.9% of Europeans. It is believed to represent some 25–40% of the difference in skin tone between Europeans and Africans, and appears to have arisen as recently as within the last 10,000 years.
Solute carrier family 45 member 2
SLC45A2
Membrane-associated transporter protein also known as solute carrier family 45 member 2 or melanoma antigen AIM1 is a protein that in humans is encoded by the SLC45A2 gene.-Function:...
(SLC45A2 or MATP) aids in the transport and processing of tyrosine
Tyrosine
Tyrosine or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is a non-essential amino acid with a polar side group...
, a precursor to melanin. It has also been shown to be a major factor in the skin color of modern Europeans through its Phe374Leu (rs16891982) variation. Like SLC24A5 it is ubiquitous in European populations but extremely rare elsewhere.
The TYR
Tyrosinase
Tyrosinase also known as monophenol monooxygenase is an enzyme that catalyses the oxidation of phenols and is widespread in plants and animals...
gene encodes the enzyme tyrosinase which is involved in the production of melanin from tyrosine. It has an allele, Ser192Tyr (rs1042602), found solely in 40–50% of Europeans and linked to light-colored skin in studies of mixed-race populations.
Oculocutaneous albinism II
OCA2
P protein is a protein that in humans is encoded by the OCA2 gene.OCA2 encodes the human homologue of the mouse p gene. The P protein is believed to be an integral membrane protein involved in small molecule transport, specifically tyrosine - a precursor of melanin...
(OCA2) assists in the regulation of pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
in melanocytes. The His615Arg (rs1800414) allele has been shown to account for about 8% of the skin tone difference between African and East Asian populations. It is found in 85% of East Asian samples and is non-existent in European and African samples.
A number of studies have found a genes linked to human skin pigmentation that have alleles with statistically significant frequencies in Asian populations. While not linked to measurements of skin tone variation directly, dopachrome tautomerase
Dopachrome tautomerase
Dopachrome tautomerase , also known as DCT, is a human gene. Its expression is regulated by the microphthalmia-associated transcription factor .-Further reading:...
(DCT or TYRP2 rs2031526), melanocortin 1 receptor
Melanocortin 1 receptor
The melanocortin 1 receptor , also known as melanocyte-stimulating hormone receptor , melanin-activating peptide receptor, or melanotropin receptor, is a G protein-coupled receptor which binds to a class of pituitary peptide hormones known as the melanocortins, of which include adrenocorticotropic...
(MC1R) Arg163Gln (rs885479) and attractin
ATRN
Attractin is a protein that in humans is encoded by the ATRN gene.Attractin is a Group XI C-type lectin.-Further reading:...
(ATRN) have been indicated as potential contributors to the evolution of light skin in East Asian populations.
Mutations in genes can cause also affect skin color through oculocutaneous albinism
Oculocutaneous albinism
Oculocutaneous albinism is a form of albinism involving the eyes , skin , and in rare instances, the hair as well.Four types of oculocutaneous albinism have been described, all caused by a disruption of melanin synthesis and all autosomal recessive disorders.Common Albinism requires genes from both...
(OCA) – a lack of pigment in the eyes, skin and sometimes hair that occurs occasionally in a very small fraction of the population. The four known types of OCA are caused by mutations of the TYR, OCA2, TYRP1
TYRP1
Tyrosinase-related protein 1, also known as TYRP1, is an enzyme which in humans is encoded by the TYRP1 gene- Function :Tyrp1 is a melanocyte-specific gene product involved in melanin synthesis. Mouse Tyrp1 possesses dihydroxyindole carboxylic acid oxidase activity, The function in human...
and SLC45A2 genes.
The gene MC1R
Melanocortin 1 receptor
The melanocortin 1 receptor , also known as melanocyte-stimulating hormone receptor , melanin-activating peptide receptor, or melanotropin receptor, is a G protein-coupled receptor which binds to a class of pituitary peptide hormones known as the melanocortins, of which include adrenocorticotropic...
is primarily responsible for determining whether pheomelanin and eumelanin is produced in humans. Mutations of this very polymorphic
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
gene, such as Arg151Sys (rs1805007), Arg160Trp (rs1805008), Asp294Sys (rs1805009), Val60Leu (rs1805005) and Val92Met (rs2228479) have been shown to cause red hair
Red hair
Red hair occurs on approximately 1–2% of the human population. It occurs more frequently in people of northern or western European ancestry, and less frequently in other populations...
and pale skin that does not tan in a small percentage of the human population. Although these alleles have differing frequencies across African, European and Asian populations, there is no evidence of positive selection for them and they do not appear to be associated with the evolution of lighter skin in Eurasian populations.
Evolution of skin color
Approximately 1.5 million years ago, the earth endured a megadrought that drove hominids from lush rainforests into arid, open landscapes. This, coupled with the loss of dense body hair, caused early human skin to endure excess UV-B radiation and xeric stress . Rogers et al. (2004) performed an examination of the variation in MC1R nucleotide sequences for people of different ancestry and compared the sequences of chimpanzees and humans from various regions of the Earth. Rogers concluded that roughly five million years ago, at the time of the evolutionary separation of chimpanzees and humans, the common ancestors of all humans had light skin that was covered by dark hair. Additionally, our closest extant relative, the chimpanzee, has light skin covered by thick body hair . Over time human hair disappeared to allow better heat dissipation through sweating and the skin tone grew darker to increase the epidermal permeability barrierStratum corneum
The stratum corneum is the outermost layer of the epidermis, consisting of dead cells that lack nuclei and organelles. The purpose of the stratum corneum is to form a barrier to protect underlying tissue from infection, dehydration, chemicals and mechanical stress...
and protect from folate depletion due to the increased exposure to sunlight. By 1.2 million years ago, around the time of homo ergaster
Homo ergaster
Homo ergaster is an extinct chronospecies of Homo that lived in eastern and southern Africa during the early Pleistocene, about 2.5–1.7 million years ago.There is still disagreement on the subject of the classification, ancestry, and progeny of H...
and homo erectus
Homo erectus
Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...
, the ancestors of all people living today had exactly the same receptor protein as modern Africans. Evolutionary pressure meant that any gene variations that resulted in lighter skin were unable to survive under the intense African sun, and human skin remained dark for the next 1.1 million years.
Approximately 70,000–100,000 years ago modern humans began to migrate away from the tropics to the north where they were exposed to less intense sunlight, possibly in part due to the need for greater use of clothing to protect against the colder climate. Under these conditions there was less photodestruction of folate and so the evolutionary pressure stopping lighter-skinned gene variants from surviving was reduced. In addition, lighter skin is able to generate more vitamin D
Vitamin D
Vitamin D is a group of fat-soluble secosteroids. In humans, vitamin D is unique both because it functions as a prohormone and because the body can synthesize it when sun exposure is adequate ....
(cholecalciferol) than darker skin so it would have represented a health benefit in reduced sunlight if there were limited sources of vitamin D. Hence the leading hypothesis for the evolution of human skin color proposes that:-
- From ~1.2 million years ago to less than 100,000 years ago, the ancestors of all people alive were from Africans which had dark skin.
- As populations began to migrate, the evolutionary constraint keeping skin dark decreased proportionally to the distance North a population migrated, resulting in a range of skin tones within northern populations.
- At some point northern populations experienced positive selection for lighter skin due to the increased production of vitamin D from sunlight and the genes for darker skin disappeared from these populations.
The genetic mutations leading to light skin, though different among East Asians and Europeans, suggest the two groups experienced a similar selective pressure due to settlement in northern latitudes.
There is a long-standing hypothesis that the selection for lighter skin due to higher vitamin D absorption occurred soon after the Out of Africa
Recent African origin of modern humans
In paleoanthropology, the recent African origin of modern humans is the most widely accepted model describing the origin and early dispersal of anatomically modern humans...
migration sometime before 40,000 years ago. A number of researchers disagree with this and suggest that the northern latitudes permitted enough synthesis of vitamin D combined with food sources from hunting to keep populations healthy, and only when agriculture was adopted was there a need for lighter skin to maximize the synthesis of vitamin D. The theory suggests that the reduction of game meat, fish, and some plants from the diet resulted in skin turning clear many thousands of years after settlement in Europe and Asia. This theory is supported by a study into the SLC24A5
SLC24A5
Sodium/potassium/calcium exchanger 5 also known as solute carrier family 24 member 5 is a protein that in humans is encoded by the SLC24A5 gene that has a major influence on natural skin colour variation. The NCKX5 protein is a member of the potassium-dependent sodium/calcium exchanger family...
gene which found that the allelle associated with light skin in Europe may have originated as recently as 6,000–10,000 years ago which is in line with the earliest evidence of farming.
One of the most recently proposed drivers of the evolution of skin pigmentation in humans is based on research that shows a superior barrier function in darkly pigmented skin . Most protective functions of the skin, including the permeability barrier and the antimicrobial barrier, reside in the stratum corneum (SC). It seems logical to surmise that the SC has undergone the most genetic change since the loss of human body hair. Natural selection would have favored mutations that protect this essential barrier; one such protective adaptation is the pigmentation of interfollicular epidermis, because it improves barrier function as compared to non-pigmented skin. In lush rainforests, however, where UV-B radiation and xeric stress were not in excess, light pigmentation would not have been nearly as detrimental. This explains the side-by-side residence of lightly pigmented and darkly pigmented peoples.
Irregular pigmentation
Uneven pigmentation of some sort affects most people, regardless of ethnic background or skin color. Skin may either appear lighter or darker than normal; there may be blotchy, uneven areas, patches of brown to gray discoloration or freckling. Skin pigmentation disorders occur because the body produces either too much or too little melanin.Increased melanin production, also known as hyperpigmentation
Hyperpigmentation
In dermatology, hyperpigmentation is the darkening of an area of skin or nails caused by increased melanin.-Causes:Hyperpigmentation may be caused by sun damage, inflammation, or other skin injuries, including those related to acne vulgaris...
, can be:
- MelasmaMelasmaMelasma is a tan or dark skin discoloration. Although it can affect anyone, melasma is particularly common in women, especially pregnant women and those who are taking oral or patch contraceptives or hormone replacement therapy medications...
describes the darkening of the skin. - Chloasma describes skin discolorations caused by hormones. These hormonal changes are usually the result of pregnancy, birth control pills or estrogen replacement therapy.
- Solar lentigo, also known as "liver spots" or "senile freckles" refers to darkened spots on the skin caused by aging and the sun. These spots are quite common in adults with a long history of unprotected sun exposure.
Aside from sun exposure and hormones, hyperpigmentation can be caused by skin damage, such as remnants of blemishes, wounds or rashes. This is especially true for those with darker skin tones.
The most typical cause of darkened areas of skin, brown spots or areas of discoloration is unprotected sun exposure. Once incorrectly referred to as liver spots
Liver spots
Liver spots are blemishes on the skin associated with aging and exposure to ultraviolet radiation from the sun...
, these pigment problems are not connected with the liver.
On lighter to medium skin tones, solar lentigenes emerge as small- to medium-sized brown patches of freckling that can grow and accumulate over time on areas of the body that receive the most unprotected sun exposure, such as the back of the hands, forearms, chest, and face. For those with darker skin colors, these discolorations can appear as patches or areas of ashen-gray skin.
Exposure to sun
MelaninMelanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...
in the skin protects the body by absorbing solar radiation. In general, the more melanin there is in the skin the more solar radiation can be absorbed. Excessive solar radiation causes direct
Direct DNA damage
Direct DNA damage can occur when DNA directly absorbs the UV-B-photon. UVB light causes thymine base pairs next to each other in genetic sequences to bond together into thymine dimers, a disruption in the strand, which reproductive enzymes cannot copy...
and indirect DNA damage
Indirect DNA damage
Indirect DNA damage occurs when a UV-photon is absorbed in the human skin by a chromophore that does not have the ability to convert the energy into harmless heat very quickly. Molecules that do not have this ability have a long lived excited state. This long lifetime leads to a high probability...
to the skin and the body naturally combats and seeks to repair the damage and protect the skin by creating and releasing further melanin into the skin's cells. With the production of the melanin, the skin color darkens, but can also cause sunburn. The tanning process can also be created by artificial UV radiation.
There are two different mechanisms involved. Firstly, the UVA-radiation creates oxidative stress, which in turn oxidizes existing melanin and leads to rapid darkening of the melanin. Secondly, there is an increase in production of melanin (melanogenesis). Melanogenesis leads to delayed tanning and first becomes visible about 72 hours after exposure. The tan that is created by an increased melanogenesis lasts much longer than the one that is caused by oxidation of existing melanin.
A person's natural skin color has an impact on their reaction to exposure to the sun. The tone of human skin can vary from a dark brown to a nearly colorless pigmentation, which may appear reddish due to the blood in the skin. Europeans generally have lighter skin, hair, and eyes than any other group, although this is not always the case. Africans generally have darker skin, hair, and eyes, although this too is not universal. For practical purposes, such as exposure time for sun tanning
Sun tanning
Sun tanning or simply tanning is the process whereby skin color is darkened or tanned. The process is most often a result of exposure to ultraviolet radiation from the sun or from artificial sources, such as a tanning bed, but can also be a result of windburn or reflected light...
, six skin types are distinguished following Fitzpatrick (1975), listed in order of decreasing lightness:
| Type | Also called | Sunburning | Tanning behavior | von Luschan scale |
|---|---|---|---|---|
| I | Very light or white, "Celtic" type | Often | Occasionally | 1–5 |
| II | Light or light-skinned European | Usually | Sometimes | 6–10 |
| III | Light intermediate or dark-skinned European | Rarely | Usually | 11–15 |
| IV | Dark intermediate, also "Mediterranean" Mediterranean race The Mediterranean race was one of the three sub-categories into which the Caucasian race and the people of Europe were divided by anthropologists in the late nineteenth and early twentieth centuries, following the publication of William Z. Ripley's book The Races of Europe... or "olive skin Olive skin Olive skin describes a skin color range of some indigenous individuals who are from the Mediterranean and some other parts of Europe, Middle East and regions of South Asia, Southeast Asia and Central Asia. It may often be skin type 3 and 4 on the Fitzpatrick scale. However, this scale measures... " and East Asian |
Rarely | Often | 16–21 |
| V | Dark or "brown Brown people Brown people or brown race is a political, racial, ethnic, societal, and cultural classification, similar to black people and white people. Like these, it is a metaphor for race based on human skin color, reflecting the fact that there are shades of skin colour intermediate between "Mediterranean" ... " type |
Very rarely | Sometimes darkens | 22–28 |
| VI | Very dark or "black Black people The term black people is used in systems of racial classification for humans of a dark skinned phenotype, relative to other racial groups.Different societies apply different criteria regarding who is classified as "black", and often social variables such as class, socio-economic status also plays a... " type |
Extremely rarely | Naturally black-brown skin | 29–36 |
Dark skin with large concentrations of melanin protects against exposure to ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light and skin cancer
Skin cancer
Skin neoplasms are skin growths with differing causes and varying degrees of malignancy. The three most common malignant skin cancers are basal cell cancer, squamous cell cancer, and melanoma, each of which is named after the type of skin cell from which it arises...
s; light-skinned people have about a tenfold greater risk of dying from skin cancer, compared with dark-skinned persons, under equal sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
exposure. Furthermore, UV-A
Black light
A black light, also referred to as a UV light, ultraviolet light, or Wood's lamp, is a lamp that emits ultraviolet radiation in the long-wave range, and little visible light...
rays from sunlight are believed to interact with folic acid
Folic acid
Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...
in ways which may damage health.
In a number of traditional societies the sun was avoided as much as possible, especially around noon when the ultraviolet radiation in sunlight is at its most intense. Midday was a time when people stayed in the shade and had the main meal followed by a nap.
While dark skin offers better protection from intense ultraviolet light, it may result in low vitamin D levels and has led to concern that darker skinned people living at relatively high latitude, such as African Americans, may have inadequate vitamin D levels. Research shows that dark-skinned people living in Western societies have lower vitamin D levels. The explanation for low vitamin D levels in dark-skinned people is thought to be that melanin
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...
in the skin hinders vitamin D synthesis. However, recent studies have found novel evidence that low vitamin D levels among people of African ancestry may be due to other reasons, such as that black women have an increase in serum parathyroid hormone
Parathyroid hormone
Parathyroid hormone , parathormone or parathyrin, is secreted by the chief cells of the parathyroid glands as a polypeptide containing 84 amino acids...
– implicated in adverse cardiovascular outcomes – at a lower vitamin D level than white women. In a large scale association study of the genetic determinants of vitamin D insufficiency in Caucasians no links to pigmentation were found.
Geographic variation
Approximately 10% of the variance in skin color occurs within groups, and ~90% occurs between groups.Because skin color has been under strong selective pressure, similar skin colors can result from convergent adaptation rather than from genetic relatedness, populations with similar pigmentation may be genetically no more similar than other widely separated groups. Furthermore, in some parts of the world in which people from different regions have mixed extensively, the connection between skin color and ancestry has been substantially weakened. In Brazil, for example, skin color is not closely associated with the percentage of recent African ancestors a person has, as estimated from an analysis of genetic variants differing in frequency among continent groups.
Considerable speculation has surrounded the possible adaptive value of other physical features characteristic of groups, such as the constellation of facial features observed in many eastern and northeastern Asians. However, any given physical characteristic generally is found in multiple groups, and demonstrating that environmental selective pressures shaped specific physical features will be difficult, since such features may have resulted from sexual selection for individuals with certain appearances or from genetic drift.
Social status and racism
According to classical scholar Frank Snowden, skin color did not determine social statusSocial status
In sociology or anthropology, social status is the honor or prestige attached to one's position in society . It may also refer to a rank or position that one holds in a group, for example son or daughter, playmate, pupil, etc....
in ancient Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
or Rome
Rome
Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...
. Relations between the major power and the subordinate state was viewed as more significant in a person's status than was their skin color.
The preferred skin tone varies by culture and has varied over time. A number of indigenous African groups, such as the Maasai, associated pale skin with being cursed or caused by evil spirits associated with witchcraft. They would abandon their children born with conditions such as albinism
Albinism
Albinism is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin...
and showed a sexual preference for darker skin.
Many cultures have historically favored lighter skin for women. In Europe, before the Industrial Revolution
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...
, pale skin was preferred and was a sign of high social status. The poorer classes worked outdoors and got darker skin from exposure to the sun, while the upper class stayed indoors and had light skin. Light skin became associated with wealth and high position. Women even went as far as to put lead-based cosmetics on their skin to artificially whiten their skin tone. However, when not strictly monitored these cosmetics caused lead poisoning
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...
. Achieving a light-skinned appearance was brought about in many other ways, including the use of arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
to whiten skin, and powders. Other methods included wearing full-length clothes when outdoors, including gloves and parasols.
Colonization and slavery by European countries inspired racism
Racism
Racism is the belief that inherent different traits in human racial groups justify discrimination. In the modern English language, the term "racism" is used predominantly as a pejorative epithet. It is applied especially to the practice or advocacy of racial discrimination of a pernicious nature...
, led by the belief that people with dark skin were uncivilized and were to be considered inferior and subordinate to the "white races", which has continued to be perpetuated in modern times. During slavery
Slavery
Slavery is a system under which people are treated as property to be bought and sold, and are forced to work. Slaves can be held against their will from the time of their capture, purchase or birth, and deprived of the right to leave, to refuse to work, or to demand compensation...
, lighter-skinned African Americans were perceived as more intelligent, cooperative, and beautiful. They were more likely to work as house slaves and were also given preferential treatment by plantation owners and the overseers. For example, they had a chance to get an education while darker African Americans worked in the fields and did not get an education. The preference for fair-skin remained prominent until the end of the Victorian era
Victorian era
The Victorian era of British history was the period of Queen Victoria's reign from 20 June 1837 until her death on 22 January 1901. It was a long period of peace, prosperity, refined sensibilities and national self-confidence...
, but the racial stereotypes about worth and beauty were still persistent in the last half of the 20th century. African American journalist Jill Nelson
Jill Nelson
Jill Nelson is a prominent African American journalist and novelist. She has written several books, including the autobiographical Volunteer Slavery: My Authentic Negro Experience, which won an American Book Award, and is currently Professor of Journalism at the City College of New York.Jill...
wrote that "to be both prettiest and black was impossible" and elaborated:
We learn as girls that in ways both subtle and obvious, personal and political, our value as females is largely determined by how we look... ... For black women, the domination of physical aspects of beauty in women's definition and value render us invisible, partially erased, or obsessed, sometimes for a lifetime, since most of us lack the major talismans of Western beauty. Black women find themselves involved in a lifelong effort to self-define in a culture that provides them no positive reflection.
In some countries, there continues to be a preference for fair or lighter skin, even in Latin American countries where whites are a minority. In Mexico, light skin is associated with power, as well as attractiveness. A dark-skinned person is more likely to be discriminated against in Brazil. Many Latin American actors and actresses have European features—blond hair, blue eyes, and pale skin. A light-skinned person is considered to be more privileged and have a higher social status; a person with light skin is considered more beautiful and it means that the person has more wealth. Skin color is such an obsession in some countries that specific words describe distinct skin tones from "hincha", Puerto Rican slang for "glass of milk" to "morena", literally "brown".
Skin whitening
Skin whitening
Skin whitening, skin lightening and skin bleaching refers to the practice of using chemical substances in an attempt to lighten skin tone or provide an even skin complexion by lessening the concentration of melanin...
products have remained prominent over time, often due to historical beliefs and perceptions about fair skin. In South and East Asian countries, light skin has traditionally been seen as more attractive and a preference for lighter skin remains prevalent. In ancient China and Japan, for example, pale skin can be traced back to ancient drawings depicting women and goddesses with fair skin tones. In ancient China, Japan, and Southeast Asia, pale skin was seen as a sign of wealth. Thus, skin whitening cosmetic products are popular in East Asia. 4 out of 10 women surveyed in Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
, Malaysia, the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
and South Korea
South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
used a skin-whitening cream, and more than 60 companies globally compete for Asia's estimated $18 billion market. Changes in regulations in the cosmetic industry led to skin care companies introducing harm free skin lighteners. This also occurs in South Asian countries, and in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, pale skin is considered more attractive and skin whitening is common. Most actors and actresses have light skin. In Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, the geisha
Geisha
, Geiko or Geigi are traditional, female Japanese entertainers whose skills include performing various Japanese arts such as classical music and dance.-Terms:...
was well known for their white painted faces, and the appeal of the , or "beautiful white", ideal leads many Japanese women to avoid any form of tanning. There are exceptions to this, with Japanese fashion trends such as ganguro
Ganguro
Ganguro is an alternative fashion trend of blonde or orange hair and tanned skin among young Japanese women that peaked in popularity around the year 2000. The Shibuya and Ikebukuro districts of Tokyo were the centers of ganguro fashion...
emphasizing almost black skin, while, in India, dark skin is sometimes associated with a lower class status and some people resort to skin bleaching to achieve a skin color they consider more socially desirable. Skin whitening products sales across the world grew from $40 to $43 billion in 2008. Skin whitening is also not uncommon in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, and several research projects have suggested a general preference for lighter skin in the African-American community. In contrast, one study on men of the Bikosso tribe in Cameroon found no preference for attractiveness of females based on lighter skin color, bringing into question the universality of earlier studies that had exclusively focused on skin color preferences among non-African populations.
It has been found that, on average, women of a given ancestry have a lighter skin tone than men of the same ancestry and that there is a sexual preference for paleness in women and darkness in men in many cultures throughout the world. In his foreword to Peter Frost's
Peter Frost (anthropologist)
Peter Frost is a Canadian anthropologist.He was awarded his Ph.D. from Université Laval in 1995.He is best known for hypotheses on the evolution of hair, eye and skin colors...
2005 Fair Women, Dark Men, University of Washington
University of Washington
University of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...
sociologist Pierre L. van den Berghe stated, "Although virtually all cultures express a marked preference for fair female skin, even those with little or no exposure to European imperialism, and even those whose members are heavily pigmented, many are indifferent to male pigmentation or even prefer men to be darker." He elaborated that popular media in the Western world has repeatedly associated blacks with "advantageous stereotypes," as much as negative ones, such as "myths that praise their athletic aptitudes amongst many other things, and often depict them as males of superior genetic inheritance".
Significant exceptions to a preference for lighter skin started to appear in Western culture mid-20th century. Though sun-tanned skin used to be associated with the sun-exposed manual labor of the lower-class, the associations became dramatically reversed during this time – a change usually credited to the trendsetting French woman Coco Chanel
Coco Chanel
Gabrielle Bonheur "Coco" Chanel was a pioneering French fashion designer whose modernist thought, menswear-inspired fashions, and pursuit of expensive simplicity made her an important figure in 20th-century fashion. She was the founder of one of the most famous fashion brands, Chanel...
making tanned skin seem fashionable, healthy, and luxurious. Today, though a preference for lighter skin remains prevalent in the United States, many within the country regard tanned skin as both more attractive and healthier than pale skin. Western mass media and popular culture continued to reinforce negative stereotypes about dark skin, but pale skin has become associated with indoor office work while tanned skin has become associated with increased leisure time, sportiness and good health that comes with wealth and higher social status. Studies indicating that the degree of tanning is directly related to how attractive a young woman is have also emerged. The election of a dark-skinned United States President and the financial success of many African-American singers and actors has challenged a number of stereotypes associated with darker skin tones. There has also been an increase in the perceived attractiveness of dark-skinned women.
See also
- Afro-textured hair
- Albinism
- ArgyriaArgyriaArgyria is a condition caused by improper exposure to chemical forms of the element silver, silver dust, or silver compounds. The most dramatic symptom of argyria is that the skin becomes blue or bluish-grey colored. Argyria may be found as generalized argyria or local argyria...
- Color terminology for race
- ComplexionComplexionComplexion refers to the natural color, texture, and appearance of the skin, especially that of the face.-History:The word "complexion" is derived from the Late Latin complexi, which initially referred in general terms to a combination of things, and later in physiological terms, to the balance of...
- Fitzpatrick scaleFitzpatrick scaleThe Fitzpatrick Scale is a numerical classification schema for the color of skin. It was developed in 1975 by Thomas B. Fitzpatrick, a Harvard dermatologist, as a way to classify the response of different types of skin to UV light...
- Human migrationHuman migrationHuman migration is physical movement by humans from one area to another, sometimes over long distances or in large groups. Historically this movement was nomadic, often causing significant conflict with the indigenous population and their displacement or cultural assimilation. Only a few nomadic...
- HyperpigmentationHyperpigmentationIn dermatology, hyperpigmentation is the darkening of an area of skin or nails caused by increased melanin.-Causes:Hyperpigmentation may be caused by sun damage, inflammation, or other skin injuries, including those related to acne vulgaris...
- Pigmentocracy
- Race
- Risks and benefits of sun exposureRisks and benefits of sun exposureThe ultraviolet radiation in sunlight, though a principal source of vitamin D3 compared to diet, is mutagenic. Supplementing diet with vitamin D3 supplies vitamin D without this mutagenic effect, but bypasses natural mechanisms that would prevent overdoses of vitamin D generated internally from...
- SunlightSunlightSunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
- Sun tanningSun tanningSun tanning or simply tanning is the process whereby skin color is darkened or tanned. The process is most often a result of exposure to ultraviolet radiation from the sun or from artificial sources, such as a tanning bed, but can also be a result of windburn or reflected light...
- Von Luschan's chromatic scaleVon Luschan's chromatic scaleVon Luschan's chromatic scale is a method of classifying skin color. It is also called the von Luschan scale or von Luschan's scale. It is named after its inventor, Felix von Luschan. The equipment consists of 36 opaque glass tiles which were compared to the subject's skin, ideally in a place which...
Other:
- Eye colorEye colorEye color is a polygenic phenotypic character and is determined by two distinct factors: the pigmentation of the eye's iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris....
- Human hair color
- Human physical appearanceHuman physical appearanceHuman physical appearance refers to the outward phenotype or look of human beings. There are infinite variations in human phenotypes, though society reduces the variability to distinct categories...
Further reading
- N Wade (August 19, 2003), "Why Humans and Their Fur Parted Ways" New York Times (Science Times). Summary of clues to the saga in which humans evolved to lose their hair and had to adjust, including turning from light skin to dark skin, together with an estimation of the time at which humans invented clothing.
- Key gene 'controls skin tone' SLC24A5 gene controls up to 38% of the tonal range in people with mixed European and West African ancestry
External links
- Computer Vision : Skin Color Based Face Tracking Examples of a face tracking in videos using a non parametric skin color model.
- Excel spreadsheet with spectrophotometry of skins of several races