During some of our (unfortunately common) discussions about race, we've talked about the muddied nature of the genetic basis for classifying large groups of people, about how large populations may carrying certain mutations at different frequencies, but that interbreeding and genetic drift make it so that the idea that a particular individual is carrying "European genes" or "African genes" or something like that is pretty meaningless. We're all carrying various combinations of many gene variants from all over the world. In fact, genetic studies suggest that there has been so much interbreeding over time that you only have to go back about 3,000 years to find the last human ancestor who passed on at least some of his genes to all (or at least the vast majority of) humans living today.
Now, we can specifically add skin color to the list of human characteristics that cannot be easily organized along racial lines. The standard theory of skin color has been that our ancestors had dark skin, and sometime after moving into Eurasia, a gene variant that lightens skin became very successful in areas that experience less UV radiation. However, there was a major flaw in the theory - namely that it was based almost entirely on genetic studies of Europeans and East Asians, with very little detailed examination of skin pigment variants in Africa. A new study in Science attempts to rectify that, and completely blows up our previous theories about skin color. In short, the study finds a huge collection of gene variants that directly affect skin color that probably have their origin in Africa. A couple of the more interesting specifics:
1. Although the famous Eurasian light-skinned gene still did probably develop there, and then drift back into Africa, other genes that are also associated with light skin among Europeans and East Asians appear to have developed in southern Africa many thousands of years earlier.
2. At least two gene variants, found in Africa, south Asia, Melanesia and Australia, associated with darker skin, appear to have developed about a half million years ago in Africa, suggesting that our latest pre-modern ancestors may have started with lighter skin. The researchers speculate that the loss of forest in favor of savanna, and a shift in our ancestors' behavior from hunting among trees to hunting on the plains may explain the success of these variants.
That second finding is especially interesting, because it adds support to the theory that non-African humans came out of Africa in multiple migrations.
To tie this back to my opening line, however, we've had some discussions about the meaning of race. This study is yet more confirmation that, while populations can be defined based on frequencies or particular variations, on an individual level, the fact that a person looks "European" and has "European" skin color means little to nothing. He's still carrying a complex combination of gene variants that all work together to determine skin color, many of which he shares with individuals in Africa, Asia, and elsewhere.
h/t @T.M.P.
Now, we can specifically add skin color to the list of human characteristics that cannot be easily organized along racial lines. The standard theory of skin color has been that our ancestors had dark skin, and sometime after moving into Eurasia, a gene variant that lightens skin became very successful in areas that experience less UV radiation. However, there was a major flaw in the theory - namely that it was based almost entirely on genetic studies of Europeans and East Asians, with very little detailed examination of skin pigment variants in Africa. A new study in Science attempts to rectify that, and completely blows up our previous theories about skin color. In short, the study finds a huge collection of gene variants that directly affect skin color that probably have their origin in Africa. A couple of the more interesting specifics:
1. Although the famous Eurasian light-skinned gene still did probably develop there, and then drift back into Africa, other genes that are also associated with light skin among Europeans and East Asians appear to have developed in southern Africa many thousands of years earlier.
2. At least two gene variants, found in Africa, south Asia, Melanesia and Australia, associated with darker skin, appear to have developed about a half million years ago in Africa, suggesting that our latest pre-modern ancestors may have started with lighter skin. The researchers speculate that the loss of forest in favor of savanna, and a shift in our ancestors' behavior from hunting among trees to hunting on the plains may explain the success of these variants.
That second finding is especially interesting, because it adds support to the theory that non-African humans came out of Africa in multiple migrations.
To tie this back to my opening line, however, we've had some discussions about the meaning of race. This study is yet more confirmation that, while populations can be defined based on frequencies or particular variations, on an individual level, the fact that a person looks "European" and has "European" skin color means little to nothing. He's still carrying a complex combination of gene variants that all work together to determine skin color, many of which he shares with individuals in Africa, Asia, and elsewhere.
h/t @T.M.P.
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