Human skin color

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"Skin pigmentation" redirects here. For animal skin pigmentation, see Biological pigment.
French actresses Romane Bohringer and Senegal-born Aïssa Maïga at the Deauville American Film Festival, 2009.

Human skin color ranges in variety from the darkest brown to the lightest pinkish-white hues. Human skin shows higher variation in color than any other single mammalian species and is the result of natural selection. Skin pigmentation in humans evolved to primarily regulate the amount of ultraviolet radiation penetrating the skin, controlling its biochemical effects.[1]

The actual skin color of different humans is affected by many substances, although the single most important substance determining human skin color is the pigment melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skinned humans. The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the haemoglobin circulating in the veins of the dermis. The red color underlying the skin becomes more visible, especially in the face, when, as consequence of physical exercise or the stimulation of the nervous system (anger, fear), arterioles dilate.[2]

Natural skin color can darken as a result of tanning due to exposure to sunlight. The leading theory is that skin color adapts to intense sunlight irradiation to provide partial protection against the ultraviolet fraction that produces damage and thus mutations in the DNA of the skin cells.[3] There is a correlation between the geographic distribution of UV radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that highlight higher amounts of UVR reflect darker-skinned populations, generally located nearer towards the equator. Areas that are far from the tropics and closer to the poles have lower concentration of UVR, which is reflected in lighter-skinned populations.[4]

In the same population it has been observed that adult human females are considerably lighter in skin pigmentation than males. Females need more calcium during pregnancy and lactation. Vitamin D, which the body synthesizes from sunlight, helps the body absorb calcium. Females evolved to have lighter skin so their bodies absorb more calcium.[5] The social significance of differences in skin color has varied across cultures and over time, as demonstrated with regard to social status and discrimination.

Contents

Melanin and genes [edit]

Main article: Melanin

Melanin is produced by cells called melanocytes 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. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms. Most are derived from the amino acid tyrosine. Eumelanin is found in hair, areola, and skin, and the hair colors grey, black, yellow, and brown. In humans, it is more abundant in people with dark skin. Pheomelanin, a pink to red hue is found in particularly large quantities in red hair,[6] the lips, nipples, glans of the penis, and vagina.[7] Both the amount and type of melanin produced is controlled by a number of genes that operate under incomplete dominance. One copy of each of the various genes is inherited from each parent. Each gene can come in several alleles, 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.

Genetics of skin color variation [edit]

See also: Human genetic variation, Race and genetics, and Human genetic clustering

Genetic studies have discovered a number of genes that affect human skin colour across different populations. These studies suggest a 3-way model for the evolution of human skin colour, with dark skin evolving in early hominids in sub-Saharan Africa and light skin evolving separately in Europe and East Asia after modern humans had expanded out of Africa.[8][9][10][11][12][13]

Dark skin [edit]

All modern humans share a common ancestor who lived around 200,000 years ago in sub-Saharan Africa.[14] Comparisons between known skin pigmentation genes in chimpanzees and modern Africans show that dark skin evolved along with the loss of body hair about 1.2 million years ago and is the ancestral state of all humans.[15] Investigations into dark skinned populations in South Asia and Melanesia indicate that skin pigmentation in these populations is due to the preservation of this ancestral state and not due to new variations on a previously lightened population.[5][16]

  • MC1R
The melanocortin 1 receptor (MC1R) gene is primarily responsible for determining whether pheomelanin and eumelanin is produced in the human body. Research shows at least 10 differences in MC1R between African and chimpanzee samples and that the gene is under strong functional constraint in Africa. This is consistent with positive selection for the high-eumelanin phenotype seen in Africa and other environments with high UV exposure.[15][16]

Light skin [edit]

For the most part, the evolution of light skin has followed different genetic paths in European and East Asian populations. Two genes however, KITLG and ASIP, have mutations associated with lighter skin that have high frequencies in both European and East Asian populations and have estimated origin dates after humans spread out of Africa but before the divergence of the European and Asian lineages.[11]

  • KITLG
The KIT ligand (KITLG) gene is involved in the permanent survival, proliferation and migration of melanocytes.[17] A mutation in this gene, A326G (rs642742[18]), 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 European populations.[19] This allele shows signs of strong positive selection outside Africa[13][20] and occurs in over 80% of European and Asian samples, compared with less than 10% in African samples.[19]
  • ASIP
Agouti signalling peptide (ASIP) acts as an inverse agonist, binding in place of alpha-MSH and thus inhibiting eumelanin production. Studies have found two alleles in the vicinity of ASIP are associated with skin color variation in humans. One, rs2424984[21] has been identified as an indicator of skin reflectance in a forensics analysis of human phenotypes across Caucasian, African-American, South Asian, East Asian, Hispanic and Native American populations[22] and is about 3 times more common in non-African populations than in Africa.[23] The other allele, 8188G (rs6058017[24]) is significantly associated with skin colour variation in African-Americans and the ancestral version occurs in only 12% of European and 28% of East Asian samples compared with 80% of West African samples.[25][26]

Europe [edit]

A number of genes have been positively associated with the skin pigmentation difference between European and non-European populations. Mutations in SLC24A5 and SLC45A2 are believed to account for the bulk of this variation and show very strong signs of selection. Research indicates they may have originated as recently within the last 20,000 years.[11][27] A variation in TYR has also been identified as a contributor.

  • SLC24A5
Solute carrier family 24 member 5 (SLC24A5) regulates calcium in melanocytes and is important in the process of melanogenesis.[28] The Thr111Ala allele (rs1426654[29]) has been shown to be a major factor in the light skin tone of Europeans compared to African-Americans, South Asians and other populations.[10][22][30] It is believed to represent as much as 25-40% of the skin tone difference between Europeans and Sub-Saharan Africans.[31] This allele has been the subject of recent selection in Europe, is fixed in European populations and absent from populations that have no European admixture.[11][32][33]
  • SLC45A2
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 one of the significant components of the skin color of modern Europeans through its Phe374Leu (rs16891982[34]) allele that has been directly correlated with skin colour variation in mixed-race populations.[10][22][30][32][35] This variation is ubiquitous in European populations but extremely rare elsewhere and shows strong signs of selection.[11][32][33][36]
  • TYR
The TYR gene encodes the enzyme tyrosinase, which is involved in the production of melanin from tyrosine. It has an allele, Ser192Tyr (rs1042602[37]), found solely in 40–50% of Europeans[10][11] and linked to light-colored skin in studies of both mixed-race South Asian[30] and African-American[38] populations.

East Asia [edit]

A number of genes known to affect skin colour have alleles that show signs of positive selection in East Asian populations. Of these only OCA2 has been directly related to skin colour measurements, while DCT, MC1R and ATTRN are marked as candidate genes for future study.

  • OCA2
Oculocutaneous albinism II (OCA2) assists in the regulation of pH in melanocytes. The His615Arg (rs1800414[39]) allele has been shown to account for about 8% of the skin tone difference between African and East Asian populations in studies of an East Asian population living in Toronto and a Chinese Han population. It shown signs of positive selection and has a frequency of 49-63% of East Asian samples but is non-existent in European and African samples.[12]
  • Candidate Genes
A number of studies have found genes linked to human skin pigmentation that have alleles with statistically significant frequencies in Chinese and East Asian populations. While not linked to measurements of skin tone variation directly, dopachrome tautomerase (DCT or TYRP2 rs2031526[40]),[41] melanocortin 1 receptor (MC1R) Arg163Gln (rs885479[42])[43] and attractin (ATRN)[10] have been indicated as potential contributors to the evolution of light skin in East Asian populations.

Tanning response [edit]

Tanning response in humans is controlled by a variety of genes. MC1R variants Arg151Sys (rs1805007[44]), Arg160Trp (rs1805008[45]), Asp294Sys (rs1805009[46]), Val60Leu (rs1805005[47]) and Val92Met (rs2228479[48]) have been associated with reduced tanning response in European and/or East Asian populations. These alleles show no signs of positive selection and only occur in relatively small numbers, reaching a peak in Europe with around 28% of the population having at least one allele of one of the variations.[16][49] A study of self-reported tanning ability and skin type in American non-Hispanic Caucasians found that SLC24A5 Phe374Leu is significantly associated with reduced tanning ability and also associated TYR Arg402Gln (rs1126809[50]), OCA2 Arg305Trp (rs1800401[51]) and a 2-SNP haplotype in ASIP (rs4911414[52] and rs1015362[53]) to skin type variation within a "fair/medium/olive" context.[35]

Albinism [edit]

Oculocutaneous albinism (OCA) is a lack of pigment in the eyes, skin and sometimes hair that occurs in a very small fraction of the population. The four known types of OCA are caused by mutations in the TYR, OCA2, TYRP1, and SLC45A2 genes.[54]

Evolution of skin color [edit]

It is theorized that about 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.[55] 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.[56] Human hair gradually disappeared to allow better heat dissipation through sweating[57] and the skin tone grew darker to increase the epidermal permeability barrier[55] and protect from folate depletion due to the increased exposure to sunlight.[3] 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.[56] Evolutionary pressure meant that any gene variations that resulted in lighter skin were less likely to survive under the intense African sun, and human skin remained dark for the next 1.1 million years.

About 70,000–100,000 years ago some 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.[57] Hence the leading hypothesis for the evolution of human skin color proposes that:

  1. From ~1.2 million years ago to less than 100,000 years ago, the ancestors of all people alive were dark-skinned Africans.
  2. 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.
  3. 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,[10] suggest the two groups experienced a similar selective pressure due to settlement in northern latitudes.[58]

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 some time 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 light many thousands of years after settlement in Europe and Asia.[59] 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 6,000–12,000 years ago,[27] which is in line with the earliest evidence of farming.[60]

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) and the researchers 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.[61]

Sexual dimorphism [edit]

In the same population it has been observed that adult human females are considerably lighter in skin pigmentation than the males. An explanation regarding this form of sexual dimorphism is related to the known fact that human females require high amounts of calcium during pregnancy and lactation. They are able to achieve this high amount of calcium by absorbing and synthesizing vitamin D in the skin, thus females must have lighter skin than males in the same environment. This is considered a form of natural selection because the offspring of females with a vitamin D and calcium deficiency could have had various birth defects such as spina bifida, which could then lead to deaths.[5]

Irregular pigmentation [edit]

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, can be:

  • Melasma 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.[62] 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.

Exposure to sun [edit]

See also: Sun tanning

Melanin 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).[63] 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:[64][65][66]

Fitzpatrick scale [edit]

Main article: Fitzpatrick scale
Type Also called Sunburning Tanning behavior Von Luschan's chromatic scale
I Light, pale white Often Occasionally 1–5
II White, fair Usually Sometimes 6–10
III Medium, white to light brown Rarely Usually 11–15
IV Olive, moderate brown Rarely Often 16–21
V Brown, dark brown Very rarely Sometimes darkens 22–28
VI Very dark brown to black Extremely rarely Naturally black-brown skin 29–36

[67]

Dark skin with large concentrations of melanin protects against ultraviolet light and skin cancers; 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 that may damage health.[68]

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.[69]

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.[70][71] Research shows that dark-skinned people living in Western societies have lower vitamin D levels.[72][73] The explanation for low vitamin D levels in dark-skinned people is thought to be that melanin in the skin hinders vitamin D synthesis.[74] Some recent studies have found novel evidence that low vitamin D levels among people of African ancestry may be due to other reasons,[75] 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.[76] In a large scale association study of the genetic determinants of vitamin D insufficiency in Caucasians no links to pigmentation were found.[77][78]

In another recent study, the vitamin D levels of traditionally living people in East Africa with skin type 6 was actually measured for the first time; it was found that the mean calcidiol level is 115 nmol/l,[79] which according to the researchers is much higher than was expected.[80]

"We expected a much higher status in these people, since they do not spend most of their time behind a PC, under a roof or totally protected by their clothing habits," Luxwolda said. "However, we were surprised that their status was even much higher than the 80 nmol/l which we had expected, since this seemed most profitable from previous studies with regard to calcium homeostasis and bone fractures."

Geographic variation [edit]

Map of indigenous skin color distribution in the world based on Von Luschan's chromatic scale.
Global racial map by Eugenicist Lothrop Stoddard in The Rising Tide of Color Against White World-Supremacy.

Approximately 10% of the variance in skin color occurs within regions, and ~90% occurs between regions.[81] 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 where people from different regions have mixed extensively, the connection between skin color and ancestry has substantially weakened.[82] 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.[83]

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.[84] However, any given physical characteristic generally is found in multiple groups,[85] and demonstrating that environmental selective pressures shaped specific physical features is difficult, since such features may result from sexual selection for individuals with certain appearances or from genetic drift.[86]

Social status, colorism and racism [edit]

Main article: Colorism
Skin colors according to von Luschan's chromatic scale

According to classical scholar Frank Snowden, skin color did not determine social status 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.[87]

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.[88]

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.[89] Women would even put lead-based cosmetics on their skin to artificially whiten their skin tone.[90] However, when not strictly monitored, these cosmetics caused lead poisoning. Achieving a light-skinned appearance was additionally brought about in various 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 colorism and racism, led by the belief that people with dark skin were uncivilized, inferior, and should be subordinate to the lighter skinned invaders. This has been perpetuated in modern times.[91] During slavery, lighter-skinned African Americans were perceived as more intelligent, cooperative, and beautiful.[92] 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[93] while darker African Americans worked in the fields and did not get an education.[94] 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 and continue in present day. African American journalist Jill Nelson wrote that, "To be both prettiest and black was impossible,"[95] 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.[95]

A Vietnamese motorcyclist wears long gloves to block the sun, despite the tropical heat.

Most actors and actresses have light skin,[96] and a preference for fair or lighter skin continues in some countries, including Latin American countries where whites are a minority.[97] In Mexico, light skin is associated with power, as well as attractiveness.[98] A dark-skinned person is more likely to be discriminated against in Brazil.[99] Many actors and actresses in Latin America and Hispanic United States have European features—blond hair, blue eyes, and pale skin.[100][101][102][103][104][105][106][107] A light-skinned person is considered more privileged and has a higher social status;[107] a person with light skin is considered more beautiful[107] and it means that the person has more wealth.[107] Skin color is such an obsession in some countries that specific words describe distinct skin tones from "jincha", Puerto Rican slang for "glass of milk" to "morena", literally "brown".[107]

In India, pale skin is considered more attractive, while dark skin is associated with a lower class status, creating a massive market for skin whitening creams.[108] Fairer skin tones also correlate, to higher-caste status in the Hindu social order - although the system is not based on skin tone.[109] Actors and actresses in Indian cinema tend to be dramatically lighter skinned than the average Indian, and Indian cinematographers use graphics and intense lighting to achieve more desirable skin tones.[110] Fairer skin tones are considered an asset in Indian marketing, with models skin tones regularly photoshopped to lighten tone.[111]

Skin whitening products have remained prominent over time, often due to historical beliefs and perceptions about fair skin. Skin whitening products sales across the world grew from $40 to $43 billion in 2008.[112] 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.[113] 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.[114] Changes in regulations in the cosmetic industry led to skin care companies introducing harm free skin lighteners. In Japan, the geisha was well known for their white painted faces, and the appeal of the bihaku (美白?), or "beautiful white", ideal leads many Japanese women to avoid any form of tanning.[115] There are exceptions to this, with Japanese fashion trends such as ganguro emphasizing almost black skin. Skin whitening is also not uncommon in Africa,[116][117] and several research projects have suggested a general preference for lighter skin in the African-American community.[118] 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.[119]

Significant exceptions to a preference for lighter skin started to appear in Western culture mid-20th century.[120] Though sun-tanned skin was once 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.[121] 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.[122][123][124][125] Western mass media and popular culture continued to reinforce negative stereotypes about dark skin,[126] but in some circles 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.[89] Studies indicating that the degree of tanning is directly related to how attractive a young woman is have also emerged.[127][128] There has also been an increase in the perceived attractiveness of dark-skinned women.[129]

See also [edit]

Other:

References [edit]

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Bibliography [edit]

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  • Harding, R; Healy, E; Ray, A; Ellis, N; Flanagan, N; Todd, C; Dixon, C; Sajantila, A et al. (2000). "Evidence for Variable Selective Pressures at MC1R". The American Journal of Human Genetics 66 (4): 1351–61. doi:10.1086/302863. PMC 1288200. PMID 10733465. 
  • Holick, Michael F. (2004). "Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease". The American journal of clinical nutrition 80 (6 Suppl): 1678S–88S. PMID 15585788. 
  • Jablonski, N; Chaplin, G (2000). "The evolution of human skin coloration". Journal of Human Evolution 39 (1): 57–106. doi:10.1006/jhev.2000.0403. PMID 10896812. 
  • Jablonski, Nina G.; Chaplin, George (2002). "Skin Deep". Scientific American 287 (4): 74–82. doi:10.1038/scientificamerican1002-74. 
  • Jablonski, Nina G. (2004). "THE EVOLUTION OF HUMAN SKIN AND SKIN COLOR". Annual Review of Anthropology 33: 585–623. doi:10.1146/annurev.anthro.33.070203.143955. 
  • Lamason, R. L.; Mohideen, MA; Mest, JR; Wong, AC; Norton, HL; Aros, MC; Jurynec, MJ; Mao, X et al. (2005). "SLC24A5, a Putative Cation Exchanger, Affects Pigmentation in Zebrafish and Humans". Science 310 (5755): 1782–6. doi:10.1126/science.1116238. PMID 16357253. 
  • Millington, G. W. M. (2006). "Proopiomelanocortin (POMC): the cutaneous roles of its melanocortin products and receptors". Clinical and Experimental Dermatology 31 (3): 407–412. doi:10.1111/j.1365-2230.2006.02128.x. PMID 16681590. 
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  • Rogers, Alan R.; Iltis, David; Wooding, Stephen (2004). "Genetic Variation at the MC1R Locus and the Time since Loss of Human Body Hair". Current Anthropology 45: 105–8. doi:10.1086/381006. 
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  • Sweet, FW (2002). "The Paleo-Etiology of Human Skin Tone". 
    • Proposes that the advent of agriculture and a grain diet low in vitamin D gave Northern Europeans their very pale skin.
    • Argues that skin tone is regulated by five genes and suggests Native Americans lost some genes in passage through the Arctic, preventing them from evolving very dark skin in equatorial America.
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External links [edit]


Human skin color
Retrieved from "http://en.wikipedia.org/w/index.php?title=Human_skin_color&oldid=555104979"