Skin color is a well-recognized adaptive trait and has been studied extensively in humans. Understanding the genetic basis of adaptation of skin color in various populations has many implications in human evolution and medicine.
Highlights:
quote: Two models of the evolutionary architecture of human pigmentation were proposed on the basis of the above results and other related studies (Fig. (Fig.2).2). One is a convergent evolution model [17, 40, 43, 49], suggesting that depigmentation has, to some degree, evolved independently in Europeans and East Asians, as different genes and variants have been suggested to explain the light skin and positive selection in these two continental groups. A recent study estimated the time of selective sweeps for the European-specific pigmentation variants to be around 11,000–19,000 years ago, after the divergence of Europeans and Asians [61]. An alternative model fits for the shared selective sweeps of Europeans and East Asians, which could possibly occur in proto-Eurasians. The onset of the sweep was estimated to be approximately 30,000 years ago, right after the “Out-of-Africa” migration, but earlier than the European-specific evolution on pigmentation [61]. The coexistence of these two models suggests a complex evolutionary history of skin color in modern humans.
quote: The hunter-gatherer populations with dark skin, short stature and curly hair have attracted much attention (Fig. (Fig.4a).4a). The genetic mechanism underlying the shared phenotypes among these geographically distant populations (collectively called Negritos or Pygmies), from Central Africa, the Andaman Islands, Southeast Asia and Oceania, are still controversial; for example, whether they were the common descent from a pre-Neolithic substrate of humanity or a consequence of convergent evolution [77, 78]. To date, most genetic studies on this issue have focused on height [78–81]. One study provided clues for convergent evolution from the view of skin pigmentation adaptation by analyzing MC1R diversity in the Melanesians [82]. This study showed that the ancestral haplotypes of MC1R are not highly conserved between Northern Island Melanesians and Africans, although both populations live in the high UV region, which is in contrast to previous findings based on very limited samples [30, 83]. Besides, a non-synonymous polymorphism, rs2228479, shows enriched derived alleles specifically in East Asians, but is not significantly associated with skin or hair pigmentation in Melanesians. Actually, the Melanesian population exhibits striking skin pigmentation variation [84], and consistently, some variants have been identified to be region-specific, which could partly explain this phenotypic variation. A notable example is a non-synonymous variant, rs387907171, in TYRP1 [85]. It is restricted to the Solomons and parts of the Bismarck Archipelago, and might contribute to the ‘blond hair’ in this region [85, 86]. These results emphasize the complex genetic architecture of pigmentation phenotypes, and also highlight the role that population history (e.g., the complex population history of the Southwest Pacific [87–89]) can play a role in influencing phenotypic diversity. Skin pigmentation studies on other modern aboriginal populations (besides Melanesians) are scarce, except for one investigating the Senoi population (an indigenous population) from the Malay Peninsula, which is an admixture of the Negrito (dark-skinned) and the southern Mongoloid from Indo-China (yellow-brown-skinned), and has a wide skin color spectrum [90]. The authors of this study found that despite the low derived allele frequency, the A111T mutation (rs1426654) in SLC24A5 is significantly associated with the light skin in Senoi, which was suspected to result from the admixture of the Mongoloid and South Asians.
quote: Another interesting issue concerning human skin color adaptation comes from the arctic people. The Inuit people, in far North Eastern Asia and the American Subarctic, have yellowish-brown skin despite the far northern latitude at which they live, unlike other populations living at the same latitude, such as the Swedes and Finnish (Fig. (Fig.4b).4b). This makes the Inuit population an exception of the latitude-correlated distribution of skin color. One possible reason is that the dark skin could protect the Inuits from the severe UV exposure because of the long daylight hours in winter and high levels of UV reflection from the snow. While the dark skin is a disadvantage for vitamin D production, plenty of vitamins including vitamin D could be compensated from their diets [91, 92]. Another cause could be the founder effect of the ancient East Asian ancestry of the Inuits, who have inhabited the arctic region since nearly 5000 years ago, and had higher melanin production than the European ancestry. However, very few genetic studies have been conducted to determine the genetic basis of dark skin in arctic populations.
quote: Recent studies on archaic hominins (e.g., Neanderthals, an extinct hominid group living in Eurasia ~400,000–28,000 years ago [102]) further improved our understanding of skin color evolution in modern humans. Neanderthals met modern humans in the Middle East ~60,000–50,000 years ago, and contributed to about 1–4% of modern human genomes [103–105]. Some pigmentation-associated genes are identified in the introgressed haplotypes from Neanderthals in modern Eurasians, such as POU2F3, BNC2 and MC1R [106, 107]. Specifically, the introgressive alleles were reported to result in light skin color, suggesting an ‘adaptive introgression’ strategy of human skin color adaptation. Other introgressive genes related to skin phenotypes include HYAL genes, which are associated with cellular responses to UV and are under strong positive selection in East Asians [108], and those involved in keratin filaments formation [109]. Although these genes are not direct determinants of skin pigmentation, they, like those pigmentation-related genes, possibly helped modern humans adapt to non-African environments.
When drawing conclusions of adaptive introgression, we are actually claiming that Neanderthals could be light-complexioned. This inference is just based on some pigmentation-associated genes or alleles identified in existing modern human populations, since visible phenotypes of Neanderthals and other extinct species are not available. However, when using some other priory genes as potential clues, different results can be obtained. For instance, the derived state of MC1R, which is responsible for pale skin, presents in Neanderthal individuals from Italy and Spain but is missing in Croatian Neanderthals and Denisova [110], suggesting skin color variation in the archaic hominins. In addition, the light skin in Neanderthals and modern Eurasians could also result from convergent evolution, rather than adaptive introgression [111].
The hypothesis of adaptive introgression seems to predate when modern human became pale – long before the late Mesolithic age, as Neanderthals went extinct around 28,000 years ago. However, we should reconsider whether the genes affecting skin color in archaic hominins indeed determined skin color in modern humans. Even if this is the case, it is also possible that modern human retained these introgressive variants until they showed some phenotypic effects under some specific strong selective pressures. Thus, more data resources and analyses are necessary to address this issue in the future.
posted
This paper is pure conjecture the existence of the pigmentation of the Inuit people falsifies the idea that UV, influences skin color. .
. The discussion about light-skinned Neanderthal is only speculation. It represents the hope that Eurocentrists can find an origin for themselves when everything else points to the original Europeans as dark skinned.
-------------------- C. A. Winters Posts: 13012 | From: Chicago | Registered: Jan 2006
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quote:Originally posted by Clyde Winters: This paper is pure conjecture the existence of the pigmentation of the Inuit people falsifies the idea that UV, influences skin color.
The inuit are not as dark as some people think. The snow is so reflective of sunlight they created what are called snow googles made out of bone. Their faces are more tanned than the rest of their bodies. Obviously to survive there the body is often covered by warm clothes.
But in addition, as the authors point out, if vitamin D in low sunlight areas is absorbed in light skinned people faster because they don't have a darker melanin barrier, inuit people don't need vitamin D from the sun because they eat a lot of oily fish which very high levels of it
There is a broad pattern in the world of people being lighter skinned as they get further away from the equator (also depending on how long they have been in a certain area and diet) You can also see this in Africa where the average Khoisan is lighter than the average Nigerian
Some igbos are lighter but they and the Inuit do not disprove the broader pattern which is much larger
Posts: 42921 | From: , | Registered: Jan 2010
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Analysis has now estimated the petroglyph, which depicts a boat, to be between 10,000 and 11,000 years old, according to the report.
“The boat is a little over four metres long. You can see the keel line and the railing line, and as you move forward you can see a really beautiful finish, forming the boat’s bows,” Gjerde told NRK, adding that the find was “incredibly exciting”.
The petroglyph is possibly the oldest in the world depicting a boat, the archaeologist told NRK.
quote:Originally posted by Clyde Winters: This paper is pure conjecture the existence of the pigmentation of the Inuit people falsifies the idea that UV, influences skin color. .
. The discussion about light-skinned Neanderthal is only speculation. It represents the hope that Eurocentrists can find an origin for themselves when everything else points to the original Europeans as dark skinned.
Totally agree with Clyde. It's a need, with every new study their inferior complex shows up - it's sad and disgusting at the same time.
-------------------- “Three things cannot be long hidden: the sun, the moon, and the truth.” Posts: 195 | From: Southern Africa(Azania) | Registered: Mar 2017
| IP: Logged |
quote:Originally posted by Clyde Winters: This paper is pure conjecture the existence of the pigmentation of the Inuit people falsifies the idea that UV, influences skin color. .
. The discussion about light-skinned Neanderthal is only speculation. It represents the hope that Eurocentrists can find an origin for themselves when everything else points to the original Europeans as dark skinned.
Totally agree with Clyde. It's a need, with every new study their inferior complex shows up - it's sad and disgusting at the same time.
-------------------- “Three things cannot be long hidden: the sun, the moon, and the truth.” Posts: 195 | From: Southern Africa(Azania) | Registered: Mar 2017
| IP: Logged |
Skin color is a well-recognized adaptive trait and has been studied extensively in humans. Understanding the genetic basis of adaptation of skin color in various populations has many implications in human evolution and medicine.
Highlights:
quote: Two models of the evolutionary architecture of human pigmentation were proposed on the basis of the above results and other related studies (Fig. (Fig.2).2). One is a convergent evolution model [17, 40, 43, 49], suggesting that depigmentation has, to some degree, evolved independently in Europeans and East Asians, as different genes and variants have been suggested to explain the light skin and positive selection in these two continental groups. A recent study estimated the time of selective sweeps for the European-specific pigmentation variants to be around 11,000–19,000 years ago, after the divergence of Europeans and Asians [61]. An alternative model fits for the shared selective sweeps of Europeans and East Asians, which could possibly occur in proto-Eurasians. The onset of the sweep was estimated to be approximately 30,000 years ago, right after the “Out-of-Africa” migration, but earlier than the European-specific evolution on pigmentation [61]. The coexistence of these two models suggests a complex evolutionary history of skin color in modern humans.
quote: The hunter-gatherer populations with dark skin, short stature and curly hair have attracted much attention (Fig. (Fig.4a).4a). The genetic mechanism underlying the shared phenotypes among these geographically distant populations (collectively called Negritos or Pygmies), from Central Africa, the Andaman Islands, Southeast Asia and Oceania, are still controversial; for example, whether they were the common descent from a pre-Neolithic substrate of humanity or a consequence of convergent evolution [77, 78]. To date, most genetic studies on this issue have focused on height [78–81]. One study provided clues for convergent evolution from the view of skin pigmentation adaptation by analyzing MC1R diversity in the Melanesians [82]. This study showed that the ancestral haplotypes of MC1R are not highly conserved between Northern Island Melanesians and Africans, although both populations live in the high UV region, which is in contrast to previous findings based on very limited samples [30, 83]. Besides, a non-synonymous polymorphism, rs2228479, shows enriched derived alleles specifically in East Asians, but is not significantly associated with skin or hair pigmentation in Melanesians. Actually, the Melanesian population exhibits striking skin pigmentation variation [84], and consistently, some variants have been identified to be region-specific, which could partly explain this phenotypic variation. A notable example is a non-synonymous variant, rs387907171, in TYRP1 [85]. It is restricted to the Solomons and parts of the Bismarck Archipelago, and might contribute to the ‘blond hair’ in this region [85, 86]. These results emphasize the complex genetic architecture of pigmentation phenotypes, and also highlight the role that population history (e.g., the complex population history of the Southwest Pacific [87–89]) can play a role in influencing phenotypic diversity. Skin pigmentation studies on other modern aboriginal populations (besides Melanesians) are scarce, except for one investigating the Senoi population (an indigenous population) from the Malay Peninsula, which is an admixture of the Negrito (dark-skinned) and the southern Mongoloid from Indo-China (yellow-brown-skinned), and has a wide skin color spectrum [90]. The authors of this study found that despite the low derived allele frequency, the A111T mutation (rs1426654) in SLC24A5 is significantly associated with the light skin in Senoi, which was suspected to result from the admixture of the Mongoloid and South Asians.
quote: Another interesting issue concerning human skin color adaptation comes from the arctic people. The Inuit people, in far North Eastern Asia and the American Subarctic, have yellowish-brown skin despite the far northern latitude at which they live, unlike other populations living at the same latitude, such as the Swedes and Finnish (Fig. (Fig.4b).4b). This makes the Inuit population an exception of the latitude-correlated distribution of skin color. One possible reason is that the dark skin could protect the Inuits from the severe UV exposure because of the long daylight hours in winter and high levels of UV reflection from the snow. While the dark skin is a disadvantage for vitamin D production, plenty of vitamins including vitamin D could be compensated from their diets [91, 92]. Another cause could be the founder effect of the ancient East Asian ancestry of the Inuits, who have inhabited the arctic region since nearly 5000 years ago, and had higher melanin production than the European ancestry. However, very few genetic studies have been conducted to determine the genetic basis of dark skin in arctic populations.
quote: Recent studies on archaic hominins (e.g., Neanderthals, an extinct hominid group living in Eurasia ~400,000–28,000 years ago [102]) further improved our understanding of skin color evolution in modern humans. Neanderthals met modern humans in the Middle East ~60,000–50,000 years ago, and contributed to about 1–4% of modern human genomes [103–105]. Some pigmentation-associated genes are identified in the introgressed haplotypes from Neanderthals in modern Eurasians, such as POU2F3, BNC2 and MC1R [106, 107]. Specifically, the introgressive alleles were reported to result in light skin color, suggesting an ‘adaptive introgression’ strategy of human skin color adaptation. Other introgressive genes related to skin phenotypes include HYAL genes, which are associated with cellular responses to UV and are under strong positive selection in East Asians [108], and those involved in keratin filaments formation [109]. Although these genes are not direct determinants of skin pigmentation, they, like those pigmentation-related genes, possibly helped modern humans adapt to non-African environments.
When drawing conclusions of adaptive introgression, we are actually claiming that Neanderthals could be light-complexioned. This inference is just based on some pigmentation-associated genes or alleles identified in existing modern human populations, since visible phenotypes of Neanderthals and other extinct species are not available. However, when using some other priory genes as potential clues, different results can be obtained. For instance, the derived state of MC1R, which is responsible for pale skin, presents in Neanderthal individuals from Italy and Spain but is missing in Croatian Neanderthals and Denisova [110], suggesting skin color variation in the archaic hominins. In addition, the light skin in Neanderthals and modern Eurasians could also result from convergent evolution, rather than adaptive introgression [111].
The hypothesis of adaptive introgression seems to predate when modern human became pale – long before the late Mesolithic age, as Neanderthals went extinct around 28,000 years ago. However, we should reconsider whether the genes affecting skin color in archaic hominins indeed determined skin color in modern humans. Even if this is the case, it is also possible that modern human retained these introgressive variants until they showed some phenotypic effects under some specific strong selective pressures. Thus, more data resources and analyses are necessary to address this issue in the future.
-------------------- “Three things cannot be long hidden: the sun, the moon, and the truth.” Posts: 195 | From: Southern Africa(Azania) | Registered: Mar 2017
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