WEBVTT - BrainStuff Classics: Did the Genes for Light Skin Colors Evolve in Europe?

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<v Speaker 1>Welcome to brain Stuff production of I Heart Radio. Hey

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<v Speaker 1>brain Stuff, Lauren vogal Bomb here with another classic episode.

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<v Speaker 1>In this one, we talk about how race really is

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<v Speaker 1>a social construct, not a biological fact, based on increasing

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<v Speaker 1>scientific evidence. Hi brain Stuff, Lauren vogal Bomb here. For ages,

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<v Speaker 1>humans have divided our species into groups based upon skin color.

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<v Speaker 1>The shade of one's complexion has been a powerful influence

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<v Speaker 1>upon human culture, affecting everything from where we live and

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<v Speaker 1>how much money we make, to how much political power

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<v Speaker 1>we have. And throughout history, racial divisions based upon skin

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<v Speaker 1>color have led to violence and war. That's all persisted

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<v Speaker 1>because people cling to the belief that people of different

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<v Speaker 1>skin colors are inherently different from one another, even though

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<v Speaker 1>scientists have been telling us for years that raises a

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<v Speaker 1>distinction that we invent in our minds, that there isn't

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<v Speaker 1>much actual difference in the genetic makeup of humans of

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<v Speaker 1>various hues. Now, an international team of researchers has published

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<v Speaker 1>a groundbreaking study in the journal Science that may demolish

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<v Speaker 1>the concept of race as a biological concept once and

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<v Speaker 1>for all. It found that genetic variations for lighter skin

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<v Speaker 1>color neither exists solely nor originate in European populations, challenges

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<v Speaker 1>the idea of using skin color as a racial classification

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<v Speaker 1>and shows that skin color may only be skin deep.

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<v Speaker 1>The scientists examined the genetic origins of skin color in Africans,

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<v Speaker 1>who vary widely in shade, from the dark skin of

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<v Speaker 1>the Dinka people in South Sudan to the light complexions

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<v Speaker 1>of the sun in South Africa. As an accompanying news

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<v Speaker 1>story in the journal Science explains, the team used a

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<v Speaker 1>light meter to measure the degree to which more than

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<v Speaker 1>two thousand individuals skin reflected light. They also gathered blood

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<v Speaker 1>samples for genetic studies. The focus upon Africans was significant

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<v Speaker 1>because most studies of the genetic underpinnings of race have

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<v Speaker 1>been based upon European subjects, a choice that's provided an

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<v Speaker 1>incomplete and perhaps misleading picture. We spoke with the studies

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<v Speaker 1>corresponding author, Sarah Tishkoff, who's a genetics and biology professor

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<v Speaker 1>at the University of Pennsylvania, via email. She said this

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<v Speaker 1>is part of a general bias that exists in human

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<v Speaker 1>genetic studies, which focus primarily on European populations. This results

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<v Speaker 1>in a bias in our knowledge about genetic factors influencing

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<v Speaker 1>both normal variable traits like skin color as well as

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<v Speaker 1>disease risk. Specifically, studies that focused only on Europeans missed

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<v Speaker 1>many of the genetic variants which we identified as associated

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<v Speaker 1>with skin color. This is because there's less genetic and

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<v Speaker 1>phenotypic i e. Skin color variation in that population compared

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<v Speaker 1>to Africans. Also, many of the variants identified in Europeans

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<v Speaker 1>are of recent origin. Prior to our study, it wasn't

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<v Speaker 1>recognized that variants associated with both light and dark skin

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<v Speaker 1>are common in Africa, and many are very old. Also,

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<v Speaker 1>our study shows that both light and dark skin has

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<v Speaker 1>been evolving in humans. Prior to our study, the emphasis

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<v Speaker 1>has been only on why light skin is adaptive in Europeans.

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<v Speaker 1>Our study changes our understanding of the evolutionary history of

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<v Speaker 1>variation in skin color. The scientists identified h etic variations

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<v Speaker 1>in four regions of the human genome that influenced skin shade.

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<v Speaker 1>Using genetic information from nearly one thousand, six hundred people.

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<v Speaker 1>They examined more than four million single nucleotide polymorphisms, that is,

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<v Speaker 1>places where the familiar DNA code made up of proteins

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<v Speaker 1>represented by the letters G, A, T, and C may

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<v Speaker 1>differ by only one letter. Those genes turn out to

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<v Speaker 1>be the ones that have spread all over the planet,

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<v Speaker 1>showing that many of the gene variations that cause light

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<v Speaker 1>skin color in Europeans actually originated in Africa. The ubiquitous

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<v Speaker 1>nature of skin color genes and their persistence over thousands

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<v Speaker 1>of years makes racial divisions seem pretty much meaningless from

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<v Speaker 1>a biological viewpoint. Tishkov said, I think that work strengthens

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<v Speaker 1>what so many geneticists and sociologists already know that race

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<v Speaker 1>cannot be defined based on genetic criteria. There have been

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<v Speaker 1>many abuses committed in the past and in the present

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<v Speaker 1>based on that assumption, so hopefully this and other studies

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<v Speaker 1>will help dispel the notion of genetically defined racial groups

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<v Speaker 1>due to genetic variants shared among populations around the world.

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<v Speaker 1>The new data also shines a light on human evolution,

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<v Speaker 1>supporting the notion of an early history migration of biologically

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<v Speaker 1>modern humans out of Africa following the southern coast of

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<v Speaker 1>Asia into Australo Melanesia, plus a secondary migration into other regions.

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<v Speaker 1>Tishkov hopes to build upon the study and explore other

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<v Speaker 1>questions that remain about the genetics of skin color. She

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<v Speaker 1>said in her email. We want to better understand the

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<v Speaker 1>biological mechanisms by which these variants are impacting skin pigmentation.

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<v Speaker 1>Our study has implications for better understanding skin pigmentation disorders

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<v Speaker 1>and melanoma risk. We're also looking at the genetic basis

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<v Speaker 1>of other adaptive traits, as well as genetic and environmental

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<v Speaker 1>factors influencing disease risk in ethnically diverse African populations. Today's

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<v Speaker 1>episode was written by Patrick J. Kaiger and produced by

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<v Speaker 1>Tristan McNeil and Tyler Klang. Or More on this and

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<v Speaker 1>lots of other topics, visit how stuffworks dot com. Brain

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