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Human skin color

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"Skin pigmentation" redirects here. For animal skin pigmentation, see Biological pigment.

Extended Coloured (Afrikaans: Kleurlinge or Bruinmense) family from South Africa showing some spectrum of human skin coloration

Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is the result of genetics (inherited from one's biological parents), exposure to the sun, disorders, or some combination thereof. Differences across populations evolved through natural selection or sexual selection, because of social norms and differences in environment, as well as regulations of the biochemical effects of ultraviolet radiation penetrating the skin.[1]

The actual skin color of different humans is affected by many substances, although the single most important substance 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-skin humans. The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the hemoglobin 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 sexual arousal, or the stimulation of the nervous system (anger, embarrassment), arterioles dilate.[2] Color is not entirely uniform across an individual's skin; for example, the skin of the palm and the sole is lighter than most other skin, and this is especially noticeable in darker-skinned people.[3]

There is a direct correlation between the geographic distribution of ultraviolet radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that receive higher amounts of UVR, generally located closer to the equator, tend to have darker-skinned populations. Areas that are far from the tropics and closer to the poles have lower intensity of UVR, which is reflected in lighter-skinned populations.[4] By the time modern Homo sapiens evolved, all humans were dark-skinned.[5][6] Some researchers suggest that human populations over the past 50,000 years have changed from dark-skinned to light-skinned and vice versa as they migrated to different UV zones,[7] and that such major changes in pigmentation may have happened in as little as 100 generations (≈2,500 years) through selective sweeps.[7][8][9] Natural skin color can also 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.[6][10]

In some populations, women are significantly lighter-skinned than men. However, in other populations, notably those of European descent, men are significantly lighter-skinned than women.[11] European women may have darker skin than European men due to the female sex hormone estrogen, which darkens light skin.[12] Women from darker-skinned populations may have evolved to lighter skin than men so their bodies could absorb more vitamin D during pregnancy, which improves calcium absorption.[13]

The social significance of differences in skin color has varied across cultures and over time, as demonstrated with regard to social status and discrimination.

Melanin and genes

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See also: Melanin

Melanin is produced by cells called melanocytes in a process called melanogenesis. Melanin is made within small membrane–bound packages called melanosomes. As they become full of melanin, they move into the slender arms of melanocytes, from where they are transferred to the keratinocytes. Under normal conditions, melanosomes cover the upper part of the keratinocytes and protect them from genetic damage. One melanocyte supplies melanin to thirty-six keratinocytes according to signals from the keratinocytes. They also regulate melanin production and replication of melanocytes.[9] People have different skin colors mainly because their melanocytes produce different amount and kinds of melanin.

The genetic mechanism behind human skin color is mainly regulated by the enzyme tyrosinase, which creates the color of the skin, eyes, and hair shades.[14][15] Differences in skin color are also attributed to differences in size and distribution of melanosomes in the skin.[9] 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 gray, black, blond, 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,[16] the lips, nipples, glans of the penis, and vagina.[17]

Both the amount and type of melanin produced is controlled by a number of genes that operate under incomplete dominance.[18] 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.

Evolution of skin color

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Further information: Melanocortin 1 receptor

Time scale of skin color evolution

[edit]

The earliest primate ancestors of humans most likely had pale non-pigmented skin, like our closest modern relative—the chimpanzee, and other great apes.[19][20][21][22][23] Loss of body hair in Homo links to the thermoregulation through perspiration heat dissipation required for activity in hot open environments[24] and endurance running.[25] Humans as primates have a particular need for this thermoregulation since unlike other mammals they lack a carotid rete that allows precooling of blood to the brain, an organ extremely sensitive to changes in body temperature.[26] Given endurance running and its needs for thermoregulation arose with H. erectus,[27] this links hairlessness with the origin of H. erectus[25] about 2 million years ago.[28][29] As hominids gradually lost their fur between 1.2 and 4 million years ago, to allow for better cooling through sweating, their naked skin was exposed to sunlight. In the tropics, natural selection favoured dark-skinned human populations as high levels of skin pigmentation protected against the harmful effects of sunlight. Indigenous populations' skin reflectance (the amount of sunlight the skin reflects) and the actual UV radiation in a particular geographic area is highly correlated, which supports this idea. Genetic evidence also supports this notion, demonstrating that around 1.2 million years ago there was a strong evolutionary pressure which acted on the development of dark skin pigmentation in early members of the genus Homo.[30] Hairlessness exposes folate circulating subcutaneously and in the dermis to degradation from UV-radiation.[31] The effect of sunlight on folic acid levels has been crucial in the development of dark skin and favored the emergence of skin pigmentation in order to protect from folate depletion due to the increased exposure to sunlight.[6][10][32][33]

In 2017, a study showed that both dark and light pigmentation alleles arose before the origin of modern humans,[34] with the older version of the variants in many cases being associated with lighter skin.[35]

With the evolution of hairless skin, abundant sweat glands, and skin rich in melanin, early humans could walk, run, and forage for food for long periods of time under the hot sun without brain damage due to overheating, giving them an evolutionary advantage over other species.[9] Research on the MC1R alleles using assumptions about past population size and an absence of population bottlenecks suggests the allele for dark skin present in modern Africans arose at least by 1.2 million years ago.[36]

This was the genotype inherited by anatomically modern humans, but retained only by part of the extant populations, thus forming an aspect of human genetic variation. About 100,000–70,000 years ago, some anatomically modern humans (Homo sapiens) began to migrate away from the tropics to the north where they were exposed to less intense sunlight. This was 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 working against the survival of lighter-skinned gene variants 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.[13] Hence the leading hypothesis for the evolution of human skin color proposes that:

  1. From the origin of hairlessness and exposure to UV-radiation to less than 100,000 years ago, archaic humans, including archaic Homo sapiens, were dark-skinned.
  2. As some Homo sapiens 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, although the bulk of humans remained dark-skinned.
  3. At some point, some 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.
  4. Subsequent migrations into different UV environments and admixture between populations have resulted in the varied range of skin pigmentations we see today.

The genetic mutations leading to light skin, though partially different among East Asians and Western Europeans,[37] suggest the two groups experienced a similar selective pressure after settlement in northern latitudes.[38]

The theory is partially supported by a study into the SLC24A5 gene which found that the allele associated with light skin in Europe "determined […] that 18,000 years had passed since the light-skin allele was fixed in Europeans" but may have originated as recently as 12,000–6,000 years ago "given the imprecision of method" ,[39] which is in line with the earliest evidence of farming.[40] Paleolithic Cro-Magnon groups, as well as Early Holocene Western and central European hunter-gatherers (Western Hunter Gatherers) have been suggested to have been dark skinned based on DNA analysis,[41][42][43] with a number of the most prominent light-skin tone gene variants found in modern Europeans being introduced by Anatolian Neolithic Farmers that migrated into Europe beginning around 9,000 years ago,[44] with selection pressure for lighter skin intensifying from the Neolithic period onwards.[44][45]

Research by Nina Jablonski suggests that an estimated time of about 10,000 to 20,000 years is enough for human populations to achieve optimal skin pigmentation in a particular geographic area but that development of ideal skin coloration may happen faster if the evolutionary pressure is stronger, even in as little as 100 generations.[7] The length of time is also affected by cultural practices such as food intake, clothing, body coverings, and shelter usage which can alter the ways in which the environment affects populations.[9]

Evolutionary model of human pigmentation in three continental populations. The colors of the branches roughly indicate the generalized skin pigmentation level of these populations.[46]

Population and admixture studies suggest a three-way model for the evolution of human skin color, with dark skin evolving in early Homo sapiens in Africa and light skin evolving only recently after modern humans had expanded out of Africa. For the most part, the evolution of light skin has followed different genetic paths in Western and Eastern Eurasian populations; however, some mutations associated with lighter skin have estimated origin dates after humans spread out of Africa but before the divergence of the two lineages.[47]

According to Crawford et al. (2017), most of the genetic variants associated with light and dark pigmentation in African populations appear to have originated more than 300,000 years ago.[48] African, South Asian and Australo-Melanesian populations also carry derived alleles for dark skin pigmentation that are not found in Europeans or East Asians.[49] Huang et al. 2021 found the existence of "selective pressure on light pigmentation in the ancestral population of Europeans and East Asians", prior to their divergence from each other. Skin pigmentation was also found to be affected by directional selection towards darker skin among Africans, as well as lighter skin among Eurasians.[50] Crawford et al. (2017) similarly found evidence for selection towards light pigmentation prior to the divergence of West Eurasians and East Asians.[49]

Functional considerations

[edit]

Elias et. al. in 2010 showed 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 and the researchers surmise that the stratum corneum 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. The authors argue that lack of significant differences between modern light-skinned and dark-skinned populations in vitamin D deficiency, early death from UV-induced cancers and birth defects — as well as instances of light and dark populations living side-by-side in areas with similar UV — suggest the standard model is insufficient to explain the strong selection drive for pigmented skin.[51] Jablonski rejects this theory on the grounds that the human tanning response is driven by UV-B exposure, not xeric stress, and that the positive selection for vitamin D production is "well-established".[6]

Genetics

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See also: Human genetic variation and Race and genetics

To some extent, skin color is determined independently of eye and hair color, as can be seen from variation in skin coloration in human populations. For the evolution of human skin color, see section above.[37][52][53][47][54][55]

For skin color, heritability is very high, even though it can be modified by exposure to sunlight.

A recent systematic study found 169 genes involved in human skin coloration. Most of the genes were involved in melanosome biogenesis, endosomal transport, and gene regulation. Notably, the function of these genes was verified in tissue culture experiments using CRISPR-Cas9 knockouts, showing that these genes are indeed involved in melanin production.[56]

Dark skin

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Main article: Dark skin

All modern humans share a common ancestor who lived around 200,000 years ago in Africa.[57] 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 that this common ancestor had dark skin.[58] 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.[13][59]

MC1R

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MC1R (rs885479)

The melanocortin 1 receptor (MC1R) gene is primarily responsible for determining whether pheomelanin and eumelanin are produced in the human body. Research shows at least 10 differences in MC1R between African and chimpanzee samples and that the gene has probably undergone a strong positive selection (a selective sweep) in early Hominins around 1.2 million years ago.[60] This is consistent with positive selection for the high-eumelanin phenotype seen in Africa and other environments with high UV exposure.[58][59]

Light skin

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Main article: Light skin
History of human skin pigmentation in Eurasia based on genetics

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. They are thought to have originated after humans spread out of Africa but before the divergence of the European and Asian lineages around 30,000 years ago.[47] Two subsequent genome-wide association studies found no significant correlation between these genes and skin color, and suggest that the earlier findings may have been the result of incorrect correction methods and small panel sizes, or that the genes have an effect too small to be detected by the larger studies.[61][62]

KITLG

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KITLG (rs1881227)

The KIT ligand (KITLG) gene is involved in the permanent survival, proliferation and migration of melanocytes.[63] A mutation in this gene, A326G (rs642742[64]), 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.[65] This allele shows signs of strong positive selection outside Africa[55][66] and occurs in over 80% of European and Asian samples, compared with less than 10% in African samples.[65]

ASIP

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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,[67] 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[68] and is about three times more common in non-African populations than in Africa.[69] The other allele, 8188G (rs6058017[70]) is significantly associated with skin color 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.[71][72]

Europe

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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. A variation in TYR has also been identified as a contributor.

Research indicates the selection for the light-skin alleles of these genes in Europeans is comparatively recent, having occurred later than 20,000 years ago and perhaps as recently as 12,000 to 6,000 years ago.[47] In the 1970s, Luca Cavalli-Sforza suggested that the selective sweep that rendered light skin ubiquitous in Europe might be correlated with the advent of farming and thus have taken place only around 6,000 years ago;[39] This scenario found support in a 2014 analysis of mesolithic (7,000 years old) hunter-gatherer DNA from La Braña, Spain, which showed a version of these genes not corresponding with light skin color.[73] In 2015 researchers analysed for light skin genes in the DNA of 94 ancient skeletons ranging from 8,000 to 3,000 years old from Europe and Russia. They found c. 8,000-year-old hunter-gatherers in Spain, Luxembourg, and Hungary were dark skinned while similarly aged hunter gatherers in Sweden were light skinned (having predominately derived alleles of SLC24A5, SLC45A2 and also HERC2/OCA2). Neolithic farmers entering Europe at around the same time were intermediate, being nearly fixed for the derived SLC24A5 variant but only having the derived SLC45A2 allele in low frequencies. The SLC24A5 variant spread very rapidly throughout central and southern Europe from about 8,000 years ago, whereas the light skin variant of SLC45A2 spread throughout Europe after 5,800 years ago.[74][75]

Some authors have expressed caution regarding the skin pigmentation predictions. According to Ju et al. (2021), in a study addressing 40,000 years of modern human history, stated:

"Relatively dark skin pigmentation in Early Upper Paleolithic Europe would be consistent with those populations being relatively poorly adapted to high-latitude conditions as a result of having recently migrated from lower latitudes. On the other hand, although we have shown that these populations carried few of the light pigmentation alleles that are segregating in present-day Europe, they may have carried different alleles that we cannot now detect."[76]

SLC24A5
[edit]

Solute carrier family 24 member 5 (SLC24A5) regulates calcium in melanocytes and is important in the process of melanogenesis.[77] The SLC24A5 gene's derived Ala111Thr allele (rs1426654[78]) has been shown to be a major factor in light skin pigmentation and is common in Western Eurasia.[68] Recent studies have found that the variant represents as much as 25–40% of the average skin tone difference between Europeans and West Africans.[37][79] This derived allele is a reliable predictor of phenotype across a range of populations.[80][81] It has been the subject of recent selection in Western Eurasia, and is fixed in European populations.[47][82][83]

SLC45A2
[edit]

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[84]) allele that has been directly correlated with skin color variation across a range of populations.[85][86][80][68][81] This variation is ubiquitous in European populations but extremely rare elsewhere and shows strong signs of selection.[82][83][87]

TYR
[edit]

The TYR gene encodes the enzyme tyrosinase, which is involved in the production of melanin from tyrosine. It has an allele, Ser192Tyr (rs1042602[88]), found solely in 40–50% of Europeans[37][47] and linked to light-colored skin in studies of South Asian[81] and African-American[89] populations.

East Asia

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

OCA2
[edit]
OCA2 (rs12913832)

Oculocutaneous albinism II (OCA2) assists in the regulation of pH in melanocytes. The OCA2 gene's derived His615Arg (rs1800414[90]) 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. This variant is essentially restricted to East Asia, with highest frequencies in Eastern East Asia (49–63%), midrange frequencies in Southeast Asia, and the lowest frequencies in Western China and some Eastern European populations.[54][91]

Candidate genes
[edit]

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[92][93]), melanocortin 1 receptor (MC1R) Arg163Gln (rs885479[94][95]) and attractin (ATRN[37]) have been indicated as potential contributors to the evolution of light skin in East Asian populations.

Tanning response

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Tanning response in humans is controlled by a variety of genes. MC1R variants Arg151Sys (rs1805007[96]), Arg160Trp (rs1805008[97]), Asp294Sys (rs1805009[98]), Val60Leu (rs1805005[99]) and Val92Met (rs2228479[100]) 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.[59][101] 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[102]), OCA2 Arg305Trp (rs1800401[103]) and a 2-SNP haplotype in ASIP (rs4911414[104] and rs1015362[105]) to skin type variation within a "fair/medium/olive" context.[106]

Albinism

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Main article: Albinism in humans

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.[107]

Age

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In hominids, the parts of the body not covered with hair, like the face and the back of the hands, start out pale in infants and turn darker as the skin is exposed to more sun. All human babies are born pale, regardless of what their adult color will be. In humans, melanin production does not peak until after puberty.[9]

The skin of children becomes darker as they go through puberty and experience the effects of sex hormones.[108] This darkening is especially noticeable in the skin of the nipples, the areola of the nipples, the labia majora in females, and the scrotum in males. In some people, the armpits become slightly darker during puberty. The interaction of genetic, hormonal, and environmental factors on skin coloration with age is still not adequately understood, but it is known that men are at their darkest baseline skin color around the age of 30, without considering the effects of tanning. Around the same age, women experience darkening of some areas of their skin.[9]

Human skin color fades with age. Humans over the age of thirty experience a decrease in melanin-producing cells by about 10% to 20% per decade as melanocyte stem cells gradually die.[109] The skin of face and hands has about twice the amount of pigment cells as unexposed areas of the body, as chronic exposure to the sun continues to stimulate melanocytes. The blotchy appearance of skin color in the face and hands of older people is due to the uneven distribution of pigment cells and to changes in the interaction between melanocytes and keratinocytes.[9]

Sexual dimorphism

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It has been observed that females are found to have lighter skin pigmentation than males in some studied populations.[13] However, in light skinned populations, namely those of European descent, women have darker skin (and eyes) than men.[11][110]

It is unknown why skin color is sexually dimorphic in some populations. White women may have darker skin than white men because the female sex hormone estrogen is known to increase skin pigmentation in lighter-skinned populations.[12] White women's skin is significantly darker than White men's, to the extent that White women have a much lower rate of skin cancer than White men.[12]

In populations where women have lighter skin than men, it has been hypothesized that the requirement for high amounts of calcium during pregnancy and lactation may be related to the dimorphism. Breastfeeding newborns, whose skeletons are growing, require high amounts of calcium intake from the mother's milk (about 4 times more than during prenatal development),[111] part of which comes from reserves in the mother's skeleton. Adequate vitamin D resources are needed to absorb calcium from the diet, and it has been shown that deficiencies of vitamin D and calcium increase the likelihood of various birth defects such as spina bifida and rickets. Natural selection may have led to females with lighter skin than males in some indigenous populations because women must get enough vitamin D and calcium to support the development of fetus and nursing infants and to maintain their own health.[9] However, some authors have cast doubt on the theory that vitamin D synthesis is related to the sexual dimorphism of human akin color in these populations.[112]

The sexes also differ in how they change their skin color with age.[11] Women can change pigmentation in certain parts of their body, such as the areola and nipples during the menstrual cycle and pregnancy. Between 50 and 70% of pregnant women will develop the "mask of pregnancy", which refers to the browning and yellowing of the cheeks, upper lips, and forehead that occurs during pregnancy.[9] This is caused by increases in the female sex hormone estrogen, and it can develop in women who take birth control pills or participate in hormone replacement therapy.[113]

Disorders of pigmentation

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Uneven pigmentation of some sort affects most people, regardless of bioethnic background or skin color. Skin may either appear lighter, or darker than normal, or lack pigmentation at all; there may be blotchy, uneven areas, patches of brown to gray discoloration or freckling. Apart from blood-related conditions such as jaundice, carotenosis, or argyria, skin pigmentation disorders generally occur because the body produces either too much or too little melanin.

Depigmentation

[edit]
Main article: Depigmentation

Albinism

[edit]

Some types of albinism affect only the skin and hair, while other types affect the skin, hair and eyes, and in rare cases only the eyes. All of them are caused by different genetic mutations. Albinism is a recessively inherited trait in humans where both pigmented parents may be carriers of the gene and pass it down to their children. Each child has a 25% chance of being albino and a 75% chance of having normally pigmented skin.[114] One common type of albinism is oculocutaneous albinism or OCA, which has many subtypes caused by different genetic mutations. Albinism is a serious problem in areas of high sunlight intensity, leading to extreme sun sensitivity, skin cancer, and eye damage.[9]

Albinism is more common in some parts of the world than in others, but it is estimated that 1 in 70 humans carry the gene for OCA. The most severe type of albinism is OCA1A, which is characterized by complete, lifelong loss of melanin production, other forms of OCA1B, OCA2, OCA3, OCA4, show some form of melanin accumulation and are less severe.[9] The four known types of OCA are caused by mutations in the TYR, OCA2, TYRP1, and SLC45A2 genes.[107]

Albinos often face social and cultural challenges (even threats), as the condition is often a source of ridicule, racism, fear, and violence. Many cultures around the world have developed beliefs regarding people with albinism. Albinos are persecuted in Tanzania by witchdoctors, who use the body parts of albinos as ingredients in rituals and potions, as they are thought to possess magical power.[115]

Vitiligo

[edit]
Former Chief Justice of India, P. Sathasivam, has vitiligo

Vitiligo is a condition that causes depigmentation of sections of skin. It occurs when melanocytes die or are unable to function. The cause of vitiligo is unknown, but research suggests that it may arise from autoimmune, genetic, oxidative stress, neural, or viral causes.[116] The incidence worldwide is less than 1%.[117] Individuals affected by vitiligo sometimes suffer psychological discomfort because of their appearance.[9]

Hyperpigmentation

[edit]

Increased melanin production, also known as hyperpigmentation, can be a few different phenomena:

  • 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.[118] 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 the sun

[edit]
See also: Sun tanning
A suntanned arm showing darker skin where it has been exposed. This pattern of tanning is often called a farmer's tan.

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, also known as IPD (immediate pigment darkening). Secondly, there is an increase in production of melanin known as melanogenesis.[119] 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. Tanning involves not just the increased melanin production in response to UV radiation but the thickening of the top layer of the epidermis, the stratum corneum.[9]

A person's natural skin color affects their reaction to exposure to the sun. Generally, those who start out with darker skin color and more melanin have better abilities to tan. Individuals with very light skin and albinos have no ability to tan.[120] The biggest differences resulting from sun exposure are visible in individuals who start out with moderately pigmented brown skin: the change is dramatically visible as tan lines, where parts of the skin which tanned are delineated from unexposed skin.[9]

Modern lifestyles and mobility have created mismatch between skin color and environment for many individuals. Vitamin D deficiencies and UVR overexposure are concerns for many. It is important for these people individually to adjust their diet and lifestyle according to their skin color, the environment they live in, and the time of year.[9] For practical purposes, such as exposure time for sun tanning, six skin types are distinguished following Fitzpatrick (1975), listed in order of decreasing lightness:

Fitzpatrick scale

[edit]
Main article: Fitzpatrick scale

The following list shows the six categories of the Fitzpatrick scale in relation to the 36 categories of the older von Luschan scale:[121][122]

Type Also called Sunburning Tanning behavior Von Luschan's chromatic scale
I Light, pale white Always Never 0–6
II White, fair Usually Minimally 7–13
III Medium white to light brown Sometimes Uniformly 14–20
IV Olive, moderate brown Rarely Easily 21–27
V Brown, dark brown Very rarely Very easily 28–34
VI Very dark brown to black Never Rarely 35–36

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.[123] 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, a practice similar to the modern siesta.

Geographic variation

[edit]

Approximately 10% of the variance in skin color occurs within regions, and approximately 90% occurs between regions.[124] 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.[125] 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.[126]

In general, people living close to the equator are highly darkly pigmented, and those living near the poles are generally very lightly pigmented. The rest of humanity shows a high degree of skin color variation between these two extremes, generally correlating with UV exposure. The main exception to this rule is in the New World, where people have only lived for about 10,000 to 15,000 years and show a less pronounced degree of skin pigmentation.[9]

In recent times, humans have become increasingly mobile as a consequence of improved technology, domestication, environmental change, strong curiosity, and risk-taking. Migrations over the last 4000 years, and especially the last 400 years, have been the fastest in human history and have led to many people settling in places far away from their ancestral homelands. This means that skin colors today are not as confined to geographical location as they were previously.[9]

Social status, colorism and racism

[edit]
Main article: Discrimination based on skin color
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. These ancient civilizations viewed relations between the major power and the subordinate state as more significant in a person's status than their skin colors.[127][page needed]

Nevertheless, some social groups favor specific skin coloring. 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.[128]

Many cultures have historically favored lighter skin for women. Before the Industrial Revolution, inhabitants of the continent of Europe preferred pale skin, which they interpreted as 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. Hence light skin became associated with wealth and high position.[129] Women would put lead-based cosmetics on their skin to whiten their skin tone artificially.[130] However, when not strictly monitored, these cosmetics caused lead poisoning. Other methods also aimed at achieving a light-skinned appearance, including the use of arsenic to whiten skin, and powders. Women would wear full-length clothes when outdoors, and would use gloves and parasols to provide shade from the sun.

Colonization and enslavement as carried out by European countries became involved with colorism and racism, associated with the belief that people with dark skin were uncivilized, inferior, and should be subordinate to lighter-skinned invaders. This belief exists to an extent in modern times as well.[131] Institutionalized slavery in North America led people to perceive lighter-skinned African-Americans as more intelligent, cooperative, and beautiful.[132] Such lighter-skinned individuals had a greater likelihood of working as house slaves and of receiving preferential treatment from plantation owners and from overseers. For example, they had a chance to get an education.[133] The preference for fair skin remained prominent until the end of the Gilded Age, but racial stereotypes about worth and beauty persisted in the last half of the 20th century and continue in the present day. African-American journalist Jill Nelson wrote that, "To be both prettiest and black was impossible,"[134] 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.[134]

A preference for fair or lighter skin continues in some countries, including Latin American countries where whites form a minority.[135] In Brazil, a dark-skinned person is more likely to experience discrimination.[136] Many actors and actresses in Latin America have European features—blond hair, blue eyes, and pale skin.[137][138] A light-skinned person is more privileged and has a higher social status;[138] a person with light skin is considered more beautiful[138] and lighter skin suggests that the person has more wealth.[138] Skin color is such an obsession in some countries that specific words describe distinct skin tones - from (for example) "jincha", Puerto Rican slang for "glass of milk" to "morena", literally "brown".[138]

In South Asia, society regards fair skin as more attractive and associates dark skin with lower class status; this results in a massive market for skin-whitening creams.[139] Fairer skin-tones also correlate to higher caste-status in the Hindu social order—although the system is not based on skin tone.[140] Actors and actresses in Indian cinema tend to have light skin tones, and Indian cinematographers have used graphics and intense lighting to achieve more "desirable" skin tones.[141] Fair skin tones are advertised as an asset in Indian marketing.[142]

Skin-whitening products have remained popular over time, often due to historical beliefs and perceptions about fair skin. Sales of skin-whitening products across the world grew from $40 billion to $43 billion in 2008.[143] In South and East Asian countries, people have traditionally seen light skin 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.[citation needed] 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.[144] Four out of ten 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.[145] Changes in regulations in the cosmetic industry led to skin-care companies introducing harm-free skin lighteners. In Japan, the geisha have a reputation 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.[146] There are exceptions to this, with Japanese fashion trends such as ganguro emphasizing tanned skin. Skin whitening is also not uncommon in Africa,[147][148] and several research projects have suggested a general preference for lighter skin in the African-American community.[149] 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.[150]

Significant exceptions to a preference for lighter skin started to appear in Western culture in the mid-20th century.[151] However, a 2010 study found a preference for lighter-skinned women in New Zealand and California.[152] 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 Frenchwoman Coco Chanel (1883–1971) presenting tanned skin as fashionable, healthy, and luxurious.[153] As of 2017, though an overall 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 or very dark skin.[154][155][156] Western mass media and popular culture continued[when?] to reinforce negative stereotypes about dark skin,[157] 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.[129] Studies have also emerged indicating that the degree of tanning is directly related to how attractive a young woman is.[158][159]

See also

[edit]

References

[edit]
  1. ^ Muehlenbein, Michael (2010). Human Evolutionary Biology. Cambridge University Press. pp. 192–213.
  2. ^ Jablonski, N.G. (2006). Skin: A Natural History. Berkeley: University of California Press.
  3. ^ Milburn, Peter B.; Sian, Corazon S.; Silvers, David N. (1982). "The color of the skin of the palms and soles as a possible clue to the pathogenesis of acral-lentiginous melanoma". American Journal of Dermatopathology. 4 (5): 429–33. doi:10.1097/00000372-198210000-00009. PMID 7149195.
  4. ^ Webb, A.R. (2006). "Who, what, where, and when: influences on cutaneous vitamin D synthesis". Progress in Biophysics and Molecular Biology. 92 (1): 17–25. doi:10.1016/j.pbiomolbio.2006.02.004. PMID 16766240.
  5. ^ Muehlenbein, Michael (2010). Human Evolutionary Biology. Cambridge University Press. pp. 192–213.
  6. ^ a b c d Jablonski, Nina; Chaplin, George (May 2017). "The colours of humanity: the evolution of pigmentation in the human lineage". Philosophical Transactions of the Royal Society B. 372 (1724): 20160349. doi:10.1098/rstb.2016.0349. PMC 5444068. PMID 28533464.
  7. ^ a b c Jablonski, Nina G. (Spring 2011). "Why Human Skin Comes in Colors" (PDF). AnthroNotes. 32 (1). Archived (PDF) from the original on 2014-02-25. Retrieved 2013-07-20.
  8. ^ "The Human Family Tree Facts". National Geographic. Archived from the original on 2013-08-05. Retrieved 2013-07-20.
  9. ^ a b c d e f g h i j k l m n o p q r Jablonski, Nina (2012). Living Color. Berkeley, Los Angeles, London: University of California Press. ISBN 978-0-520-25153-3.
  10. ^ a b Jablonski, N. G.; Chaplin, G. (2010). "Colloquium Paper: Human skin pigmentation as an adaptation to UV radiation". Proceedings of the National Academy of Sciences. 107 (Suppl 2): 8962–8. Bibcode:2010PNAS..107.8962J. doi:10.1073/pnas.0914628107. PMC 3024016. PMID 20445093.
  11. ^ a b c Frost, Peter (2007). "Human skin‐color sexual dimorphism: A test of the sexual selection hypothesis". American Journal of Physical Anthropology. 133 (1): 779–780. doi:10.1002/ajpa.20555. ISSN 0002-9483. p.779: "It is perhaps significant that this sex difference seems to disappear or even reverse itself when skin reflectance is close to the physiological maximum, notably in Dutch and Belgian subjects (Leguebe, 1961; van Rijn-Tournel, 1966; Rigters-Aris, 1973)...Even after adolescence, age-related noise continues to muddy the data. Human skin may change more slowly during adulthood, but it does change. In particular, there is some evidence that skin color becomes less sexually dimorphic after 40, with some papers finding that women become nonsignificantly darker than men (Chamla and De´moulin, 1978; Mori and Tokuhashi, 1956; Rigters-Aris, 1973)."
  12. ^ a b c "Researchers discover genetic causes of higher melanoma risk in men". ScienceDaily. 21 July 2016. Retrieved 15 February 2021. "Meanwhile, several studies have shown that female hormones promote the production of melanin, the pigment that protects the skin from the sun. Indeed, "estrogen could be the reason why women have a darker skin tone, even when the genotypes of both sexes are the same, meaning that their risk of skin cancer is lower. So much so that skin cancer is much more prevalent in men," explains Bárbara Hernando, fellow researcher at the Melanogen research group and coauthor of the study."
  13. ^ a b c d Jablonski, Nina; Chaplin, George (2000). "The evolution of human skin coloration" (PDF). Journal of Human Evolution. 39 (1): 57–106. doi:10.1006/jhev.2000.0403. PMID 10896812. Archived from the original (PDF) on January 5, 2015.
  14. ^ Sturm, R. A. (2006). "A golden age of human pigmentation genetics". Trends in Genetics. 22 (9): 464–469. doi:10.1016/j.tig.2006.06.010. PMID 16857289.
  15. ^ Sturm, R. A.; Teasdale, R. D.; Box, N. F. (2001). "Human pigmentation genes: Identification, structure and consequences of polymorphic variation". Gene. 277 (1–2): 49–62. doi:10.1016/s0378-1119(01)00694-1. PMID 11602344.
  16. ^ Ito, S.; Wakamatsu, K. (Dec 2011). "Diversity of human hair pigmentation as studied by chemical analysis of eumelanin and pheomelanin". J Eur Acad Dermatol Venereol. 25 (12): 1369–1380. doi:10.1111/j.1468-3083.2011.04278.x. PMID 22077870. S2CID 5121042.
  17. ^ "pheomelanin". MetaCyc. Archived from the original on 2015-01-21. Retrieved 2012-02-17.
  18. ^ Schneider, Patricia (2003). "The Genetics and Evolution of Skin Color: The Case of Desiree's Baby". RACE—The Power of an Illusion. Public Broadcasting Service. Archived from the original on 6 May 2015. Retrieved 14 April 2015.
  19. ^ Jablonski, N. G.; Chaplin, G. (2000). "The evolution of human skin coloration". Journal of Human Evolution. 39 (1): 57–106. doi:10.1006/jhev.2000.0403. ISSN 0047-2484. PMID 10896812.
  20. ^ Wade, Nicholas (2003-08-19). "Why Humans and Their Fur Parted Ways". The New York Times. ISSN 0362-4331. Retrieved 2024-01-13.
  21. ^ Elias, Peter M.; Menon, Gopinathan; Wetzel, Bruce K.; Williams, John (Jack) W. (2009). "Evidence that stress to the epidermal barrier influenced the development of pigmentation in humans". Pigment Cell & Melanoma Research. 22 (4): 420–434. doi:10.1111/j.1755-148X.2009.00588.x. ISSN 1755-1471. PMC 2843517. PMID 19508412.
  22. ^ Greaves, Mel (2014-04-22). "Was skin cancer a selective force for black pigmentation in early hominin evolution?". Proceedings of the Royal Society B: Biological Sciences. 281 (1781): 20132955. doi:10.1098/rspb.2013.2955. ISSN 0962-8452. PMC 3953838. PMID 24573849.
  23. ^ Alex, Bridget (2019-01-28). "Why Did Darker and Lighter Human Skin Colors Evolve?". Discover Magazine. Retrieved 2024-04-16.
  24. ^ Ruxton, Graeme D.; Wilkinson, David M. (2011-12-12). "Avoidance of overheating and selection for both hair loss and bipedality in hominins". Proceedings of the National Academy of Sciences. 108 (52): 20965–20969. Bibcode:2011PNAS..10820965R. doi:10.1073/pnas.1113915108. ISSN 0027-8424. PMC 3248486. PMID 22160694.
  25. ^ a b Ruxton, Graeme D.; Wilkinson, David M. (2011). "Thermoregulation and endurance running in extinct hominins: Wheeler's models revisited". Journal of Human Evolution. 61 (2): 169–175. doi:10.1016/j.jhevol.2011.02.012. ISSN 0047-2484. PMID 21489604.
  26. ^ Bruner, Emiliano; Mantini, Simone; Musso, Fabio; De La Cuétara, José Manuel; Ripani, Maurizio; Sherkat, Shahram (2010-11-30). "The evolution of the meningeal vascular system in the human genus: From brain shape to thermoregulation". American Journal of Human Biology. 23 (1): 35–43. doi:10.1002/ajhb.21123. ISSN 1042-0533. PMID 21120884. S2CID 24603018.
  27. ^ Bramble, Dennis M.; Lieberman, Daniel E. (2004). "Endurance running and the evolution of Homo" (PDF). Nature. 432 (7015): 345–352. Bibcode:2004Natur.432..345B. doi:10.1038/nature03052. ISSN 0028-0836. PMID 15549097. S2CID 2470602.
  28. ^ Branda, Richard F.; Eaton, John W. (1978-08-18). "Skin Color and Nutrient Photolysis: An Evolutionary Hypothesis". Science. 201 (4356): 625–626. Bibcode:1978Sci...201..625B. doi:10.1126/science.675247. ISSN 0036-8075. PMID 675247.
  29. ^ Herries, Andy I. R.; Martin, Jesse M.; Leece, A. B.; Adams, Justin W.; Boschian, Giovanni; Joannes-Boyau, Renaud; Edwards, Tara R.; Mallett, Tom; Massey, Jason; Murszewski, Ashleigh; Neubauer, Simon; Pickering, Robyn; Strait, David S.; Armstrong, Brian J.; Baker, Stephanie; Caruana, Matthew V.; Denham, Tim; Hellstrom, John; Moggi-Cecchi, Jacopo; Mokobane, Simon; Penzo-Kajewski, Paul; Rovinsky, Douglass S.; Schwartz, Gary T.; Stammers, Rhiannon C.; Wilson, Coen; Woodhead, Jon; Menter, Colin (2020-04-03). "Contemporaneity of Australopithecus , Paranthropus , and early Homo erectus in South Africa". Science. 368 (6486). doi:10.1126/science.aaw7293. ISSN 0036-8075. PMID 32241925.
  30. ^ Nina, Jablonski (2004). "The evolution of human skin and skin color". Annual Review of Anthropology. 33: 585–623. doi:10.1146/annurev.anthro.33.070203.143955. S2CID 53481281.
  31. ^ Rocha, Jorge (2019-07-30). "The Evolutionary History of Human Skin Pigmentation". Journal of Molecular Evolution LLC. 88 (1): 77–87. doi:10.1007/s00239-019-09902-7. ISSN 0022-2844. PMID 31363820. S2CID 198998060.
  32. ^ Muehlenbein, Michael (2010). Human Evolutionary Biology. Cambridge University Press. pp. 192–213.
  33. ^ Gina, Kirchweger. "The Biology of Skin Color: Black and White". Evolution Library. PBS. Archived from the original on 16 February 2013. Retrieved 10 December 2012.
  34. ^ Crawford, Nicholas G.; Kelly, Derek E.; Hansen, Matthew E. B.; Beltrame, Marcia H.; Fan, Shaohua; Bowman, Shanna L.; Jewett, Ethan; Ranciaro, Alessia; Thompson, Simon; Lo, Yancy; Pfeifer, Susanne P.; Jensen, Jeffrey D.; Campbell, Michael C.; Beggs, William; Hormozdiari, Farhad (2017-11-17). "Loci associated with skin pigmentation identified in African populations". Science. 358 (6365). doi:10.1126/science.aan8433. ISSN 0036-8075. PMC 5759959. PMID 29025994.
  35. ^ "Penn-led Study Identifies Genes Responsible for Diversity of Human Skin Colors". Penn Today. 2017-10-12. Retrieved 2024-04-16.
  36. ^ Rogers, Iltis & Wooding 2004b, p. 107.
  37. ^ a b c d e Norton, H. L.; Kittles, R. A.; Parra, E.; McKeigue, P.; Mao, X.; Cheng, K.; Canfield, V. A.; Bradley, D. G.; McEvoy, B.; Shriver, M. D. (2006). "Genetic Evidence for the Convergent Evolution of Light Skin in Europeans and East Asians". Molecular Biology and Evolution. 24 (3): 710–22. doi:10.1093/molbev/msl203. PMID 17182896.
  38. ^ Juzeniene, Asta; Setlow, Richard; Porojnicu, Alina; Steindal, Arnfinn Hykkerud; Moan, Johan (2009). "Development of different human skin colors: A review highlighting photobiological and photobiophysical aspects". Journal of Photochemistry and Photobiology B: Biology. 96 (2): 93–100. doi:10.1016/j.jphotobiol.2009.04.009. PMID 19481954.
  39. ^ a b Gibbons, A. (2007). "European Skin Turned Pale Only Recently, Gene Suggests" (PDF). Science. 316 (5823): 364a. doi:10.1126/science.316.5823.364a. PMID 17446367. S2CID 43290419. Archived from the original (PDF) on 2010-11-03. Retrieved 2011-01-26. "a suggestion made 30 years ago by Stanford University geneticist L. Luca Cavalli-Sforza … that the early immigrants to Europe … survived on ready-made sources of vitamin D in their diet. But when farming spread in the past 6,000 years, he argued, Europeans had fewer sources of vitamin D in their food and needed to absorb more sunlight to produce the vitamin in their skin."
  40. ^ Tellier, Luc-Normand (2009). Urban world history: an economic and geographical perspective. p. 26. ISBN 978-2-7605-1588-8.
  41. ^ Posth, Cosimo; Yu, He; Ghalichi, Ayshin; Rougier, Hélène; Crevecoeur, Isabelle; Huang, Yilei; Ringbauer, Harald; Rohrlach, Adam B.; Nägele, Kathrin; Villalba-Mouco, Vanessa; Radzeviciute, Rita; Ferraz, Tiago; Stoessel, Alexander; Tukhbatova, Rezeda; Drucker, Dorothée G. (2023-03-02). "Palaeogenomics of Upper Palaeolithic to Neolithic European hunter-gatherers". Nature. 615 (7950): 117–126. doi:10.1038/s41586-023-05726-0. ISSN 0028-0836. PMC 9977688. PMID 36859578.
  42. ^ Brace, Selina; Diekmann, Yoan; Booth, Thomas J.; Faltyskova, Zuzana; Rohland, Nadin; Mallick, Swapan; Ferry, Matthew; Michel, Megan; Oppenheimer, Jonas; Broomandkhoshbacht, Nasreen; Stewardson, Kristin; Walsh, Susan; Kayser, Manfred; Schulting, Rick; Craig, Oliver E.; Sheridan, Alison; Pearson, Mike Parker; Stringer, Chris; Reich, David; Thomas, Mark G.; Barnes, Ian (2019), "Ancient genomes indicate population replacement in Early Neolithic Britain", Nature Ecology & Evolution, 3 (5): 765–771, Bibcode:2019NatEE...3..765B, doi:10.1038/s41559-019-0871-9, PMC 6520225, PMID 30988490 Supplementary Material (p.18-19): "This individual has light or blue/green eye colour, it is not light blue, there are elements of brown/yellow in the eye to give a proposed perceived green colour. Better coverage at the low sequenced marker would clarify this but blue/hazel cannot be ruled out. It is certainly not a brown eyed or clear blue-eyed individual... Skin pigmentation [assumptions about missing information omitted] The following range for skin pigmentation prediction is possible for this individual with these parameters:... Intermediate 0.152 - 0.038 Dark-Black 0.848 - 0.962 Final prediction: Dark/Dark-to-Black skin If we omit the three missing alleles, our tool produces 0.752 and 0.248 probabilities for the intermediate and dark-black category respectively, changing the prediction ranges to 0.752- 0.038 and 0.248-0.962. However, note that this completely removes the locus from the prediction model; hence the prediction will not perform optimally (how the prediction model was made). It is therefore best to have some allele present to infer the most probable range for Cheddar Man and we derive the ranges above from the extreme allele constellations only. Explanation: The missing loci certainly impact on this prediction; however, utilizing the input of all ancestral alleles is the preferred option over the use of the derived alleles at these loci – hence 0.152 for intermediate and 0.848 for Dark-to-Black would be the most probable profile. That being said a broad range is present in both the intermediate and dark-black categories due to the missing loci. Also, this effect of skipping a skin pigmentation prediction category with regards probability values, tends to be observed more often in admixed individuals. What is important to note is the input of the dark-black prediction is significant on the intermediate category and therefore it is acceptable to propose a dark complexion individual over an intermediate/light prediction even though the intermediate range is present. It is unlikely that this individual has the darkest possible pigmentation, but it cannot be ruled out. Better sequencing coverage would clarify to what degree this individual has a dark complexion."
  43. ^ González-Fortes, Gloria; Jones, Eppie R.; Lightfoot, Emma; Bonsall, Clive; Lazar, Catalin; Grandal-d’Anglade, Aurora; Garralda, María Dolores; Drak, Labib; Siska, Veronika; Simalcsik, Angela; Boroneanţ, Adina; Vidal Romaní, Juan Ramón; Vaqueiro Rodríguez, Marcos; Arias, Pablo; Pinhasi, Ron (June 2017). "Paleogenomic Evidence for Multi-generational Mixing between Neolithic Farmers and Mesolithic Hunter-Gatherers in the Lower Danube Basin". Current Biology. 27 (12): 1801–1810.e10. doi:10.1016/j.cub.2017.05.023. PMC 5483232. PMID 28552360.
  44. ^ a b Ju, Dan; Mathieson, Iain (2021-01-05). "The evolution of skin pigmentation-associated variation in West Eurasia". Proceedings of the National Academy of Sciences. 118 (1). doi:10.1073/pnas.2009227118. ISSN 0027-8424. PMC 7817156. PMID 33443182.
  45. ^ Lazaridis, Iosif; Alpaslan-Roodenberg, Songül; Acar, Ayşe; Açıkkol, Ayşen; Agelarakis, Anagnostis; Aghikyan, Levon; Akyüz, Uğur; Andreeva, Desislava; Andrijašević, Gojko; Antonović, Dragana; Armit, Ian; Atmaca, Alper; Avetisyan, Pavel; Aytek, Ahmet İhsan; Bacvarov, Krum (2022-08-26). "A genetic probe into the ancient and medieval history of Southern Europe and West Asia". Science. 377 (6609): 940–951. doi:10.1126/science.abq0755. ISSN 0036-8075. PMC 10019558. PMID 36007020.
  46. ^ Deng, Lian; Xu, Shuhua (15 June 2017). "Adaptation of human skin color in various populations". Hereditas. 155 (1): 1. doi:10.1186/s41065-017-0036-2. ISSN 1601-5223. PMC 5502412. PMID 28701907.
  47. ^ a b c d e f Belezal, Sandra; Santos, A. M.; McEvoy, B.; Alves, I.; Martinho, C.; Cameron, E.; Shriver, M. D.; Parra, E. J.; Rocha, J. (2012). "The timing of pigmentation lightening in Europeans". Molecular Biology and Evolution. 30 (1): 24–35. doi:10.1093/molbev/mss207. PMC 3525146. PMID 22923467. Archived from the original on 2012-08-29.
  48. ^ "Genes responsible for diversity of human skin colors identified". ScienceDaily. 2017.
  49. ^ a b Crawford, Nicholas (2017). "Loci associated with skin pigmentation identified in African populations". Science. 358 (6365): eaan8433. doi:10.1126/science.aan8433. PMC 5759959. PMID 29025994.
  50. ^ Huang, Xin (2021). "Dissecting dynamics and differences of selective pressures in the evolution of human pigmentation". Biology Open. 10 (2). doi:10.1242/bio.056523. PMC 7888712. PMID 33495209.
  51. ^ Elias, PM; Menon, G; Wetzel, BK; Williams, J (2010). "Barrier Requirements as the Evolutionary "Driver" of Epidermal Pigmentation in Humans". American Journal of Human Biology. 22 (4): 526–537. doi:10.1002/ajhb.21043. PMC 3071612. PMID 20209486.
  52. ^ McEvoy, B. (2006). "The genetic architecture of normal variation in human pigmentation: an evolutionary perspective and model". Human Molecular Genetics. 15 (2): 176–181. doi:10.1093/hmg/ddl217. PMID 16987881.
  53. ^ Sturm, R. A. (2009). "Molecular genetics of human pigmentation diversity". Human Molecular Genetics. 18 (R1): 9–17. doi:10.1093/hmg/ddp003. PMID 19297406.
  54. ^ a b Edwards, Melissa; Bigham, Abigail; Tan, Jinze; Li, Shilin; Gozdzik, Agnes; Ross, Kendra; Jin, Li; Parra, Esteban J. (2010). McVean, Gil (ed.). "Association of the OCA2 Polymorphism His615Arg with Melanin Content in East Asian Populations: Further Evidence of Convergent Evolution of Skin Pigmentation". PLOS Genetics. 6 (3): e1000867. doi:10.1371/journal.pgen.1000867. PMC 2832666. PMID 20221248.
  55. ^ a b Lao, O.; De Gruijter, J. M.; Van Duijn, K.; Navarro, A.; Kayser, M. (May 2007). "Signatures of Positive Selection in Genes Associated with Human Skin Pigmentation as Revealed from Analyses of Single Nucleotide Polymorphisms". Annals of Human Genetics. 71 (3): 354–369. doi:10.1111/j.1469-1809.2006.00341.x. PMID 17233754. S2CID 20657917.
  56. ^ Bajpai, Vivek K.; Swigut, Tomek; Mohammed, Jaaved; Naqvi, Sahin; Arreola, Martin; Tycko, Josh; Kim, Tayne C.; Pritchard, Jonathan K.; Bassik, Michael C.; Wysocka, Joanna (2023-08-11). "A genome-wide genetic screen uncovers determinants of human pigmentation". Science. 381 (6658): eade6289. doi:10.1126/science.ade6289. ISSN 0036-8075. PMC 10901463. PMID 37561850. S2CID 260776374.
  57. ^ Soares, P; Ermini, L; Thomson, N; Mormina, M; Rito, T; Röhl, A; Salas, A; Oppenheimer, S; MacAulay, V; Richards, M. B. (June 2009). "Correcting for purifying selection: an improved human mitochondrial molecular clock". Am. J. Hum. Genet. 84 (6): 740–59. doi:10.1016/j.ajhg.2009.05.001. PMC 2694979. PMID 19500773.
  58. ^ a b Rogers, Alan R.; Iltis, David; Wooding, Stephen (2004b). "Genetic Variation at the MC1R Locus and the Time since Loss of Human Body Hair". Current Anthropology. 45 (6): 105–108. doi:10.1086/381006. JSTOR 381006. S2CID 224795768.
  59. ^ a b c Harding, R; Healy, E; Ray, A; Ellis, N; Flanagan, N; Todd, C; Dixon, C; Sajantila, A; Jackson, I; Birch-Machin, Mark A.; Rees, Jonathan L. (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.
  60. ^ Rogers, Alan R.; Iltis, David; Wooding, Stephen (2004a). "Genetic variation at the MC1R locus and the time since loss of human body hair". Current Anthropology. 45 (1): 105–124. doi:10.1086/381006. S2CID 224795768.
  61. ^ Beleza, Sandra; Johnson, Nicholas A.; Candille, Sophie I.; Absher, Devin M.; Coram, Marc A.; Lopes, Jailson; Campos, Joana; Araújo, Isabel Inês; Anderson, Tovi M.; Vilhjálmsson, Bjarni J.; Nordborg, Magnus; Correia e Silva, António; Shriver, Mark D.; Rocha, Jorge; Barsh, Gregory S.; Tang, Hua (March 2013). "Genetic Architecture of Skin and Eye Color in an African-European Admixed Population". PLOS Genetics. 9 (3): e1003372. doi:10.1371/journal.pgen.1003372. PMC 3605137. PMID 23555287.
  62. ^ Candille, Sophie I.; Absher, Devin M.; Beleza, Sandra; Bauchet, Marc; McEvoy, Brian; Garrison, Nanibaa' A.; Li, Jun Z.; Myers, Richard M.; Barsh, Gregory S.; Tang, Hua; Shriver, Mark D. (31 October 2012). "Genome-Wide Association Studies of Quantitatively Measured Skin, Hair, and Eye Pigmentation in Four European Populations". PLOS ONE. 7 (10): e48294. Bibcode:2012PLoSO...748294C. doi:10.1371/journal.pone.0048294. PMC 3485197. PMID 23118974.
  63. ^ Wehrle-Haller, Bernhard (2003). "The Role of Kit-Ligand in Melanocyte Development and Epidermal Homeostasis". Pigment Cell Research. 16 (3): 287–96. doi:10.1034/j.1600-0749.2003.00055.x. PMID 12753403.
  64. ^ Reference SNP(refSNP) Cluster Report: rs642742 **clinically associated** Archived 2018-03-28 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30). Retrieved 2011-02-27.
  65. ^ a b Miller, Craig T.; Beleza, Sandra; Pollen, Alex A.; Schluter, Dolph; Kittles, Rick A.; Shriver, Mark D.; Kingsley, David M. (2007). "cis-Regulatory Changes in Kit Ligand Expression and Parallel Evolution of Pigmentation in Sticklebacks and Humans". Cell. 131 (6): 1179–89. doi:10.1016/j.cell.2007.10.055. PMC 2900316. PMID 18083106.
  66. ^ Pickrell, J. K.; Coop, G; Novembre, J; Kudaravalli, S; Li, J. Z.; Absher, D; Srinivasan, B. S.; Barsh, G. S.; Myers, R. M.; Feldman, M. W.; Pritchard, J. K. (2009). "Signals of recent positive selection in a worldwide sample of human populations". Genome Research. 19 (5): 826–837. doi:10.1101/gr.087577.108. PMC 2675971. PMID 19307593.
  67. ^ Reference SNP(refSNP) Cluster Report: rs2424984 Archived 2016-05-01 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30). Retrieved 2011-02-27.
  68. ^ a b c Valenzuela, Robert K.; Henderson, Miquia S.; Walsh, Monica H.; Garrison, Nanibaa' A.; Kelch, Jessica T.; Cohen-Barak, Orit; Erickson, Drew T.; John Meaney, F.; Bruce Walsh, J.; Cheng, Keith C.; Ito, Shosuke; Wakamatsu, Kazumasa; Frudakis, Tony; Thomas, Matthew; Brilliant, Murray H. (2010). "Predicting Phenotype from Genotype: Normal Pigmentation". Journal of Forensic Sciences. 55 (2): 315–22. doi:10.1111/j.1556-4029.2009.01317.x. PMC 3626268. PMID 20158590. Archived from the original on 2013-06-13.
  69. ^ HapMap: SNP report for rs2424984. Hapmap.ncbi.nlm.nih.gov (2009-10-19). Retrieved 2011-02-27.
  70. ^ "Reference SNP (refSNP) Cluster Report: rs6058017 ** With Pathogenic allele **". Ncbi.nlm.nih.gov. 2006-01-28. Archived from the original on 2015-02-03. Retrieved 2015-02-03.
  71. ^ Bonilla, C; Boxill, L. A.; Donald, S. A.; Williams, T; Sylvester, N; Parra, E. J.; Dios, S; Norton, H. L.; Shriver, M. D.; Kittles, R. A. (2005). "The 8818G allele of the agouti signaling protein (ASIP) gene is ancestral and is associated with darker skin color in African Americans". Human Genetics. 116 (5): 402–6. doi:10.1007/s00439-004-1251-2. PMID 15726415. S2CID 12910408.
  72. ^ Zeigler-Johnson, C; Panossian, S; Gueye, S. M.; Jalloh, M; Ofori-Adjei, D; Kanetsky, P. A. (2004). "Population Differences in the Frequency of the Agouti Signaling Protein g.8818A>G Polymorphism". Pigment Cell Research. 17 (2): 185–187. doi:10.1111/j.1600-0749.2004.00134.x. PMID 15016309.
  73. ^ Olalde, Iñigo; Allentoft, Morten E.; Sánchez-Quinto, Federico; Santpere, Gabriel; Chiang, Charleston W. K.; Degiorgio, Michael; Prado-Martinez, Javier; Rodríguez, Juan Antonio; Rasmussen, Simon; Quilez, Javier; Ramírez, Oscar; Marigorta, Urko M.; Fernández-Callejo, Marcos; Prada, María Encina; Encinas, Julio Manuel Vidal; Nielsen, Rasmus; Netea, Mihai G.; Novembre, John; Sturm, Richard A.; Sabeti, Pardis; Marquès-Bonet, Tomàs; Navarro, Arcadi; Willerslev, Eske; Lalueza-Fox, Carles (2014). "Derived immune and ancestral pigmentation alleles in a 7,000-year-old Mesolithic European". Nature. 507 (7491): 225–228. Bibcode:2014Natur.507..225O. doi:10.1038/nature12960. PMC 4269527. PMID 24463515. The La Braña individual carries ancestral alleles in several skin pigmentation genes, suggesting that the light skin of modern Europeans was not yet ubiquitous in Mesolithic time
  74. ^ Gibbons, Ann (2 April 2015). "How Europeans evolved white skin". Science. doi:10.1126/science.aab2435. Archived from the original on 2015-04-14. Retrieved 13 April 2015.
  75. ^ Mathieson, I.; Lazaridis, I.; Rohland, N.; Mallick, S.; Llamas, B.; Pickrell, J.; Meller, H.; Rojo Guerra, M. A.; Krause, J.; Anthony, D.; Brown, D.; Lalueza Fox, C.; Cooper, A.; Alt, K. W.; Haak, W.; Patterson, N.; Reich, D. (2015). "Eight thousand years of natural selection in Europe". bioRxiv 10.1101/016477.
  76. ^ Ju, Dan; Mathieson, Ian (2021). "The evolution of skin pigmentation-associated variation in West Eurasia". PNAS. 118 (1): e2009227118. Bibcode:2021PNAS..11809227J. doi:10.1073/pnas.2009227118. PMC 7817156. PMID 33443182. Relatively dark skin pigmentation in Early Upper Paleolithic Europe would be consistent with those populations being relatively poorly adapted to high-latitude conditions as a result of having recently migrated from lower latitudes. On the other hand, although we have shown that these populations carried few of the light pigmentation alleles that are segregating in present-day Europe, they may have carried different alleles that we cannot now detect.
  77. ^ Ginger, R. S.; Askew, S. E.; Ogborne, R. M.; Wilson, S.; Ferdinando, D.; Dadd, T.; Smith, A. M.; Kazi, S.; Szerencsei, R. T.; Winkfein, R. J.; Schnetkamp, P. P. M.; Green, M. R. (2007). "SLC24A5 Encodes a trans-Golgi Network Protein with Potassium-dependent Sodium-Calcium Exchange Activity That Regulates Human Epidermal Melanogenesis". Journal of Biological Chemistry. 283 (9): 5486–95. doi:10.1074/jbc.M707521200. PMID 18166528.
  78. ^ "rs1426654 RefSNP Report". ncbi.nlm.nih.gov. Retrieved 15 February 2021.
  79. ^ Lamason, R. L.; Mohideen, MA; Mest, JR; Wong, AC; Norton, HL; Aros, MC; Jurynec, MJ; Mao, X; Humphreville, VR; Humbert, J. E.; Sinha, S; Moore, J. L.; Jagadeeswaran, P; Zhao, W; Ning, G; Makalowska, I; McKeigue, P. M.; O'Donnell, D; Kittles, R; Parra, E. J.; Mangini, N. J.; Grunwald, D. J.; Shriver, M. D.; Canfield, V. A.; Cheng, K. C. (2005). "SLC24A5, a Putative Cation Exchanger, Affects Pigmentation in Zebrafish and Humans". Science. 310 (5755): 1782–6. Bibcode:2005Sci...310.1782L. doi:10.1126/science.1116238. PMID 16357253. S2CID 2245002.
  80. ^ a b López, Saioa (5 August 2014). "The Interplay between Natural Selection and Susceptibility to Melanoma on Allele 374F of SLC45A2 Gene in a South European Population". PLOS ONE. 9 (8): e104367. Bibcode:2014PLoSO...9j4367L. doi:10.1371/journal.pone.0104367. PMC 4122405. PMID 25093503.
  81. ^ a b c Stokowski, R; Pant, P; Dadd, T; Fereday, A; Hinds, D; Jarman, C; Filsell, W; Ginger, R; Green, M; Van Der Ouderaa, Frans J.; Cox, David R. (2007). "A Genomewide Association Study of Skin Pigmentation in a South Asian Population". The American Journal of Human Genetics. 81 (6): 1119–32. doi:10.1086/522235. PMC 2276347. PMID 17999355.
  82. ^ a b Soejima, Mikiko; Koda, Yoshiro (2006). "Population differences of two coding SNPs in pigmentation-related genes SLC24A5 and SLC45A2". International Journal of Legal Medicine. 121 (1): 36–9. doi:10.1007/s00414-006-0112-z. PMID 16847698. S2CID 11192076.
  83. ^ a b Ang, K. C.; Ngu, M. S.; Reid, K. P.; Teh, M. S.; Aida, Z. S.; Koh, D. X.; Berg, A; Oppenheimer, S; Salleh, H; Clyde, M. M.; Md-Zain, B. M.; Canfield, V. A.; Cheng, K. C. (2012). "Skin Color Variation in Orang Asli Tribes of Peninsular Malaysia". PLOS ONE. 7 (8): e42752. Bibcode:2012PLoSO...742752A. doi:10.1371/journal.pone.0042752. PMC 3418284. PMID 22912732.
  84. ^ "rs16891982 RefSNP Report - dbSNP - NCBI". www.ncbi.nlm.nih.gov. Retrieved 2022-10-02.
  85. ^ Adhikari, Kaustubh (21 January 2019). "A GWAS in Latin Americans highlights the convergent evolution of lighter skin pigmentation in Eurasia". Nature Communications. 10 (1): 358. Bibcode:2019NatCo..10..358A. doi:10.1038/s41467-018-08147-0. PMC 6341102. PMID 30664655.
  86. ^ Deng, Lian (15 June 2017). "Adaptation of human skin color in various populations". Hereditas. 155: 1. doi:10.1186/s41065-017-0036-2. PMC 5502412. PMID 28701907.
  87. ^ Soejima, M; Tachida, H; Ishida, T; Sano, A; Koda, Y (January 2006). "Evidence for Recent Positive Selection at the Human AIM1 Locus in a European Population". Molecular Biology and Evolution. 23 (1): 179–188. doi:10.1093/molbev/msj018. PMID 16162863.
  88. ^ Reference SNP(refSNP) Cluster Report: rs1042602 **clinically associated** Archived 2016-04-16 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30). Retrieved 2011-02-27.
  89. ^ Shriver, MD; Parra, EJ; Dios, S; Bonilla, C; Norton, H; Jovel, C; Pfaff, C; Jones, C; Massac, A; Cameron, N; Baron, A; Jackson, T; Argyropoulos, G; Jin, L; Hoggart, CJ; McKeigue, PM; Kittles, RA (2003). "Skin pigmentation, biogeographical ancestry and admixture mapping" (PDF). Human Genetics. 112 (4): 387–399. doi:10.1007/s00439-002-0896-y. PMID 12579416. S2CID 7877572. Archived from the original (PDF) on 2012-04-15.
  90. ^ "rs1800414 RefSNP Report". ncbi.nlm.nih.gov. Retrieved 15 February 2021.
  91. ^ Donnelly, Michael P.; Paschou, Peristera; Grigorenko, Elena; Gurwitz, David; Barta, Csaba; Lu, Ru-Band; Zhukova, Olga V.; Kim, Jong-Jin; Siniscalco, Marcello; New, Maria; Li, Hui; Kajuna, Sylvester L. B.; Manolopoulos, Vangelis G.; Speed, William C.; Pakstis, Andrew J.; Kidd, Judith R.; Kidd, Kenneth K. (2012). "A global view of the OCA2-HERC2 region and pigmentation" (PDF). Human Genetics. 131 (5): 683–696. doi:10.1007/s00439-011-1110-x. PMC 3325407. PMID 22065085. Archived from the original (PDF) on 2013-11-03.
  92. ^ "rs2031526 RefSNP Report". ncbi.nlm.nih.gov. Retrieved 15 February 2021.
  93. ^ Myles, S; Somel, M; Tang, K; Kelso, J; Stoneking, M (2006). "Identifying genes underlying skin pigmentation differences among human populations". Human Genetics. 120 (5): 613–621. doi:10.1007/s00439-006-0256-4. PMID 16977434. S2CID 32371450.
  94. ^ Reference SNP(refSNP) Cluster Report: rs885479 Archived 2016-09-19 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30). Retrieved 2011-02-27.
  95. ^ Shi, Peng; Lu, Xue Mei; Luo, Huai Rong; Xiang-Yu, Jin-Gong; Zhang, Ya Ping (2001). "Melanocortin-1 receptor gene variants in four Chinese ethnic populations". Cell Research. 11 (1): 81–4. doi:10.1038/sj.cr.7290070. PMID 11305330.
  96. ^ Reference SNP(refSNP) Cluster Report: rs1805007 Archived 2016-11-08 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30).
  97. ^ Reference SNP(refSNP) Cluster Report: rs1805008 Archived 2016-11-08 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30).
  98. ^ Reference SNP(refSNP) Cluster Report: rs1805009 Archived 2016-11-08 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30).
  99. ^ Reference SNP(refSNP) Cluster Report: rs1805005 Archived 2018-03-28 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30).
  100. ^ Reference SNP(refSNP) Cluster Report: rs2228479 Archived 2018-03-28 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30).
  101. ^ Valverde, P; Healy, E; Jackson, I; Rees, J. L.; Thody, A. J. (1995). "Variants of the melanocyte-stimulating hormone receptor gene are associated with red hair and fair skin in humans". Nature Genetics. 11 (3): 328–30. doi:10.1038/ng1195-328. PMID 7581459. S2CID 7980311.
  102. ^ "Reference SNP (refSNP) Cluster Report: rs1126809 ** With Pathogenic allele **". Ncbi.nlm.nih.gov. 2006-01-28. Archived from the original on 2015-07-22. Retrieved 2015-02-03.
  103. ^ "Reference SNP (refSNP) Cluster Report: rs1800401 ** With Pathogenic allele **". Ncbi.nlm.nih.gov. 2006-01-28. Archived from the original on 2015-02-03. Retrieved 2015-02-03.
  104. ^ Reference SNP(refSNP) Cluster Report: rs4911414 **clinically associated** Archived 2018-03-28 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30). Retrieved 2011-02-27.
  105. ^ Reference SNP(refSNP) Cluster Report: rs1015362 **clinically associated** Archived 2018-03-28 at the Wayback Machine. Ncbi.nlm.nih.gov (2008-12-30). Retrieved 2011-02-27.
  106. ^ Nan, Hongmei; Kraft, Peter; Hunter, David J.; Han, Jiali (2009). "Genetic variants in pigmentation genes, pigmentary phenotypes, and risk of skin cancer in Caucasians". International Journal of Cancer. 125 (4): 909–17. doi:10.1002/ijc.24327. PMC 2700213. PMID 19384953.
  107. ^ a b Albinism, Oculocutaneous, Type IA; OCA1A Archived 2010-08-03 at the Wayback Machine, Johns Hopkins University
  108. ^ "Everything You Wanted to Know About Puberty (for Teens) - Nemours KidsHealth". kidshealth.org. Retrieved 2022-05-24.
  109. ^ Tobin, D. J. (2009). "Aging of the Hair Follicle Pigmentation System". International Journal of Trichology. 1 (2): 83–93. doi:10.4103/0974-7753.58550. PMC 2938584. PMID 20927229.
  110. ^ Candille, Sophie I.; Absher, Devin M.; Beleza, Sandra; Bauchet, Marc; McEvoy, Brian; Garrison, Nanibaa' A.; Li, Jun Z.; Myers, Richard M.; Barsh, Gregory S.; Tang, Hua; Shriver, Mark D. (2012). "Genome-Wide Association Studies of Quantitatively Measured Skin, Hair, and Eye Pigmentation in Four European Populations". PLOS ONE. 7 (10): e48294. Bibcode:2012PLoSO...748294C. doi:10.1371/journal.pone.0048294. PMC 3485197. PMID 23118974.
  111. ^ Kovacs, Christine (2008). "Vitamin D in pregnancy and lactation: maternal, fetal, and neonatal outcomes from human and animal studies". American Journal of Clinical Nutrition. 88 (2): 520S–528S. doi:10.1093/ajcn/88.2.520S. PMID 18689394.
  112. ^ Madrigal, Lorena; Kelly, William (2007). "Human skin‐color sexual dimorphism: A test of the sexual selection hypothesis". American Journal of Physical Anthropology. 132 (3): 470–482. doi:10.1002/ajpa.20453. ISSN 0002-9483. "Although Jablonski (2004) and Jablonski and Chaplin (2000) argued that pro- duction of vitamin D is the main evolutionary explanation for the origin of light skin in areas of solar radiation, others, such as Aoki (2002), were less convinced, still pointing to the lack of paleopathological evidence of rick- ets (Webb and Holick, 1988)..."
  113. ^ Costin, G. E.; Hearing, V. J. (2007). "Human skin pigmentation: Melanocytes modulate skin color in response to stress". FASEB Journal. 21 (4): 976–994. doi:10.1096/fj.06-6649rev. PMID 17242160. S2CID 10713500.
  114. ^ Cummings (2011). Human Heridity Principles and Issues'. Cengage 9th edition. Retrieved 2014-02-16.
  115. ^ BBC (27 July 2008). "Tanzania Albinos Targeted Again". BBC News (online edition). Retrieved 2010-01-03.
  116. ^ Halder, RM; Chappell, JL (2009). "Vitiligo update". Seminars in Cutaneous Medicine and Surgery. 28 (2): 86–92. doi:10.1016/j.sder.2009.04.008. PMID 19608058.
  117. ^ Nath, S. K.; Majumder, P. P.; Nordlund, J. J. (1994). "Genetic epidemiology of vitiligo: multilocus recessivity cross-validated". American Journal of Human Genetics. 55 (5): 981–90. PMC 1918341. PMID 7977362.
  118. ^ Cutis, August 2005, pp 19–23
  119. ^ Agar, N; Young, A. R. (2005). "Melanogenesis: a photoprotective response to DNA damage?". Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis. 571 (1–2): 121–132. doi:10.1016/j.mrfmmm.2004.11.016. PMID 15748643.
  120. ^ Fitzpatrick, T. B. (2003). "Normal skin color and general considerations of pigmentary disorders". Fitzpatrick's Dermatology in General Medicine. New York: McGraw-Hill. pp. 819–825.
  121. ^ Jablonski, Nina (2010). Muehlenbein, Michael P. (ed.). Human Evolutionary Biology. Cambridge University Press. p. 177. ISBN 978-0-521-87948-4. Retrieved 24 May 2016.
  122. ^ "Fitzpatrick Skin Type" (PDF). Australian Radiation Protection and Nuclear Safety Agency. Archived from the original (PDF) on 31 March 2016. Retrieved 24 May 2016.
  123. ^ Vorobey, P; Steindal, AE; Off, MK; Vorobey, A; Moan, J (2006). "Influence of human serum albumin on photodegradation of folic acid in solution". Photochemistry and Photobiology. 82 (3): 817–22. doi:10.1562/2005-11-23-RA-739. PMID 16454580. S2CID 36351333.
  124. ^ Relethford, J. H. (2002). "Apportionment of global human genetic diversity based on craniometrics and skin color". American Journal of Physical Anthropology. 118 (4): 393–8. CiteSeerX 10.1.1.473.5972. doi:10.1002/ajpa.10079. PMID 12124919. S2CID 8717358.
  125. ^ Parra, E. J.; Kittles, R. A.; Shriver, M. D. (2004). "Implications of correlations between skin color and genetic ancestry for biomedical research". Nature Genetics. 36 (11): S54–S60. doi:10.1038/ng1440. PMID 15508005. S2CID 13712615.
  126. ^ Parra, F. C.; Amado, R. C.; Lambertucci, J. R.; Rocha, J.; Antunes, C. M.; Pena, S. D. J. (2003). "Color and genomic ancestry in Brazilians". Proceedings of the National Academy of Sciences. 100 (1): 177–182. Bibcode:2003PNAS..100..177P. doi:10.1073/pnas.0126614100. PMC 140919. PMID 12509516.
  127. ^ Snowden, Frank M. (1970). Blacks in Antiquity: Ethiopians in the Greco-Roman Experience. Harvard University Press. ISBN 978-0-674-07626-6.
  128. ^ Africa: Dispelling Myths about Albinism Archived 2011-06-22 at the Wayback Machine, Pambazuka News, 10 September 2009
  129. ^ a b Kruszelnicki, Karl (March 1, 2001). "News in Science: Skin Colour 1". abc.net.au. Archived from the original on December 28, 2013. Retrieved May 25, 2014.
  130. ^ Agredano (February 2006). "Accessibility to air travel correlates strongly with increasing melanoma incidence". Melanoma Research. 16 (1): 77–81. doi:10.1097/01.cmr.0000195696.50390.23. PMID 16432460. S2CID 6462810.
  131. ^ Hall, Ron (1997). "The Psychogenesis of Color Based Racism: Implications of Projection for Dark-Skinned Puertorriqueños" (PDF). Julian Samora Research Institute, Michigan State University. Archived from the original (PDF) on January 6, 2011. Retrieved 2012-09-25.
  132. ^ "What Are "Good Looks"?". Kenyon College. Archived from the original on 2014-10-13. Retrieved 2014-03-23.
  133. ^ "The Paper Bag Test". St. Petersburg Times. 2003-08-31. Archived from the original on 2013-08-06. Retrieved 2014-03-23.
  134. ^ a b Nelson, Jill (1997). "Straight, No Chaser—How I Became a Grown-Up Black Woman— WHO'S THE FAIREST OF THEM ALL?" (PDF). The New York Times. Archived (PDF) from the original on 2011-05-10. Retrieved 2009-11-06. As a girl and young woman, hair, body, and color were society's trinity in determining female beauty and identity... 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.
  135. ^ "Documentary, Studies Renew Debate About Skin Color's Impact". Pittsburgh Post-Gazette. 2006-12-26. Archived from the original on 2014-01-30. Retrieved 2014-03-23.
  136. ^ "Racism Takes Many Hues". Miami Herald. 2007-08-24. Archived from the original on 2013-02-23. Retrieved 2014-03-23.
  137. ^ Quinonez, Ernesto (2003-06-19). "Y Tu Black Mama Tambien". Archived from the original on 2008-10-27. Retrieved 2008-05-02.; Fletcher, Michael A. (2000-08-03). "The Blond, Blue-Eyed Face of Spanish TV". Washington Post. Retrieved 2012-08-18.; "Blonde, Blue-Eyed Euro-Cute Latinos on Spanish TV". Latinola.com. 2010-10-24. Archived from the original on 2017-09-02. Retrieved 2012-08-18.; "Latinos Not Reflected on Spanish TV". Vidadeoro.com. 2010-10-25. Archived from the original on 2017-09-09. Retrieved 2012-08-18.; "What are Telenovelas?—Hispanic Culture". Bellaonline.com. Archived from the original on 2017-06-22. Retrieved 2012-08-18.; Fletcher, Michael A. (2000-08-06). "Racial Bias Charged On Spanish-Language TV". Sun-Sentinel. Archived from the original on 2011-09-13. Retrieved 2012-08-18.; "Black Electorate". Black Electorate. 2 January 2001. Archived from the original on 20 June 2017. Retrieved 2012-08-18.
  138. ^ a b c d e Jones, Vanessa E. (2004-08-19). "Pride or Prejudice?". Boston Globe. Archived from the original on 2011-05-12. Retrieved 2014-03-23.
  139. ^ Sidner, Sara (9 September 2009). "Skin whitener advertisements labeled racist". CNN. Archived from the original on 12 September 2009. Retrieved 2009-09-11. 'We always have a complex towards a white skin, towards foreign skin or foreign hair,' Jawed Habib says. Habib should know. He owns a chain of 140 salons located in India and across the world. 'We Indian people, we Asian people are more darker, so we want to look more fair.' … A marketing study found sales for skin whitening creams have jumped more than 100 percent in rural India and sales for male grooming products are increasing 20 percent annually.
  140. ^ Saxena, Shobhan (26 April 2009). "Caste: Racism in all but name?". The Times of India. New Delhi. Archived from the original on 22 May 2013. Retrieved 2012-09-20.
  141. ^ Vaidyanathan, Rajini (5 June 2012). "Has skin whitening in India gone too far?". BBC News. London. Archived from the original on 6 September 2012. Retrieved 2012-09-20.
  142. ^ Lakshmi, Rama (27 January 2008). "In India's Huge Marketplace, Advertisers Find Fair Skin Sells". Washington Post. Washington DC. Archived from the original on 10 October 2013. Retrieved 2012-09-20.
  143. ^ "Bleaching Creams: Fade to Beautiful?". Northwestern University. 2010-03-10. Archived from the original on July 20, 2011. Retrieved 2014-03-23.
  144. ^ "Skin Deep: Dying to be White". CNN. 2002-05-15. Archived from the original on 2010-04-08. Retrieved 2014-03-23.
  145. ^ Skin whitening big business in Asia Archived 2010-07-26 at the Wayback Machine. Pri.Org. Retrieved 2011-02-27.
  146. ^ Mowbray, Nicole (4 April 2004). "Japanese girls choose whiter shade of pale". Guardian Unlimited. London. Retrieved 2010-05-24.
  147. ^ "The Heavy Cost of Light Skin". BBC News. 2000-04-18. Archived from the original on 2014-03-23. Retrieved 2014-03-23.
  148. ^ "Mirror mirror on the wall, who is the FAIREST of them all?" Skin lightening Archived 2010-09-10 at the Wayback Machine. Scienceinafrica.co.za. Retrieved 2011-02-27.
  149. ^ Color Counts: "... it is evident that differing color holds considerable importance within the black community and is measurably influencing self-esteem, prestige, and marital status." |USA Today (Society for the Advancement of Education) Archived 2014-03-30 at the Wayback Machine. Retrieved 2012-09-25.
  150. ^ Dixson, Barnaby J.; Dixson, Alan F.; Morgan, Bethan; Anderson, Matthew J. (2006). "Human Physique and Sexual Attractiveness: Sexual Preferences of Men and Women in Bakossiland, Cameroon". Archives of Sexual Behavior. 36 (3): 369–75. doi:10.1007/s10508-006-9093-8. PMID 17136587. S2CID 40115821.
  151. ^ Singer, Merrill; Beyer, Hans (28 July 2008). Killer Commodities: Public Health and the Corporate Production of Harm. AltaMira Press. p. 151. ISBN 978-0-7591-0979-7. Retrieved 2009-09-11. Harris investigated the history of the parasol... everywhere ordinary people were forbidden to protect themselves with such devices "pallid skin became a marker of upper-class status". At the beginning of the 20th Century, in the United States, lighter-skinned people avoided the sun... Tanned skin was considered lower class.
  152. ^ Dixson, Barnaby J.; Dixson, Alan F.; Bishop, Phil J.; Parish, Amy (June 2010). "Human Physique and Sexual Attractiveness in Men and Women: A New Zealand–U.S. Comparative Study". Archives of Sexual Behavior. 39 (3): 798–806. doi:10.1007/s10508-008-9441-y. PMID 19139985. S2CID 33112678. men expressed preferences for lighter skinned female figures in New Zealand and California
  153. ^ Koskoff, Sharon (28 May 2007). Art Deco of the Palm Beaches. Arcadia Publishing. p. 2. ISBN 978-0-7385-4415-1. Retrieved 2009-09-11. In 1920s France, the caramel-skinned entertainer Josephine Baker became a Parisian idol. Concurrently, fashion designer Coco Chanel was "bronzed" while cruising on a yacht. A winter tan became a symbol of the leisure class and showed you could afford to travel to exotic climates.
  154. ^ Geller, A. C.; Colditz, G.; Oliveria, S.; Emmons, K.; Jorgensen, C.; Aweh, G. N.; Frazier, A. L. (1 June 2002). "Use of Sunscreen, Sunburning Rates, and Tanning Bed Use Among More Than 10 000 US Children and Adolescents". Pediatrics. 109 (6): 1009–1014. doi:10.1542/peds.109.6.1009. PMID 12042536.
  155. ^ Broadstock, Marita; Borland, Ron; Gason, Robyn (2006-07-31). "Effects of Suntan on Judgements of Healthiness and Attractiveness by Adolescents". Journal of Applied Social Psychology. 22 (2): 157–172. doi:10.1111/j.1559-1816.1992.tb01527.x. Archived from the original on 2013-01-05.
  156. ^ Leary, Mark R.; Jones, Jody L. (2006-07-31). "The Social Psychology of Tanning and Sunscreen Use: Self-Presentational Motives as a Predictor of Health Risk". Journal of Applied Social Psychology. 23 (17): 1390–1406. doi:10.1111/j.1559-1816.1993.tb01039.x. Archived from the original on 2013-01-05.
  157. ^ Balkaran, Steven (1999). "Mass Media and Racism". Archived from the original on 2011-11-24.
  158. ^ Leary, Mark R.; Jones, Jody L. (1993). "The Social Psychology of Tanning and Sunscreen Use: Self-Presentational Motives as a Predictor of Health Risk". Journal of Applied Social Psychology. 23 (17): 1390–406. doi:10.1111/j.1559-1816.1993.tb01039.x.
  159. ^ Banerjee, S. C.; Campo, S; Greene, K (2008). "Fact or wishful thinking? Biased expectations in "I think I look better when I'm tanned"". American Journal of Health Behavior. 32 (3): 243–52. doi:10.5993/AJHB.32.3.2. PMID 18067464. Archived from the original on 2014-03-24.

Further reading

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