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Speaker 1: Welcome to brain Stuff from how Stuff Works High brain

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Speaker 1: Stuff Lauren Vogel bomb here for ages. Humans have divided

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Speaker 1: our species into groups based upon skin color. The shade

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Speaker 1: of one's complexion has been a powerful influence upon human culture,

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Speaker 1: affecting everything from where we live and how much money

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Speaker 1: we make, to how much political power we have, and

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Speaker 1: throughout history, racial divisions based upon skin color have led

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Speaker 1: to violence and war. That's all persisted because people cling

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Speaker 1: to the belief that people of different skin colors are

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Speaker 1: inherently different from one another, even though scientists have been

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Speaker 1: telling us for years that race is a distinction that

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Speaker 1: we invent in our minds, that there isn't much actual

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Speaker 1: difference in the genetic makeup of humans of various hues. Now,

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Speaker 1: an international team of researchers has published a groundbreaking study

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Speaker 1: in the journal Science that may demolish the concept of

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Speaker 1: race as a biological concept once and for all. It

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Speaker 1: found that genetic variations for lighter skin color neither exists

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Speaker 1: solely nor originate in European populations, challenges the idea of

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Speaker 1: using skin color as a racial classification and shows that

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Speaker 1: skin color may only be skin deep. The scientists examined

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Speaker 1: the genetic origins of skin color in Africans, who vary

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Speaker 1: widely in shade, from the dark skin of the Dinka

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Speaker 1: people in South Sudan to the light complexions of the

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Speaker 1: sun in South Africa. As an accompanying news story in

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Speaker 1: the journal Science explains, the team used a light meter

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Speaker 1: to measure the degree to which more than two thousand

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Speaker 1: individuals skin reflected light. They also gathered blood samples for

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Speaker 1: genetic studies. The focus upon Africans was significant because most

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Speaker 1: studies of the genetic underpinnings of race have been based

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Speaker 1: upon European subjects, a choice that's provided an incomplete and

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Speaker 1: perhaps misleading picture. We spoke with the studies corresponding author,

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Speaker 1: Sarah Tishkoff, who's a genetics and biology professor at the

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Speaker 1: University of Pennsylvania, via email. She said this is part

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Speaker 1: of a general bias that exists in human genetic studies,

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Speaker 1: which focus primarily on European populations. This results in a

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Speaker 1: bias in our knowledge about genetic factors influencing both normal

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Speaker 1: variable traits like skin color as well as disease risk. Specifically,

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Speaker 1: studies that focused only on Europeans missed many of the

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Speaker 1: genetic variants which we identified as associated with skin color.

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Speaker 1: This is because there's less genetic and phenotypic I. E.

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Speaker 1: Skin color variation in that population compared to Africans. Also,

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Speaker 1: many of the variants identified in Europeans are of recent origin.

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Speaker 1: Prior to our study, it wasn't recognized that variants associated

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Speaker 1: with both light and dark skin are common in Africa,

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Speaker 1: and many are very old. Also, our study shows that

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Speaker 1: both light and dark skin has been evolving in humans.

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Speaker 1: Prior to our study, that emphasis has been only on

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Speaker 1: why light skin is adaptive in Europeans. Our study changes

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Speaker 1: our understanding of the evolutionary history of variation and skin color.

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Speaker 1: The scientists identified eight genetic variations in four regions of

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Speaker 1: the human genome that influenced skin shade. Using genetic information

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Speaker 1: from nearly one thousand, six hundred people, They examined more

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Speaker 1: than four million single nucleotide polymorphisms. That is, places where

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Speaker 1: the familiar DNA code made up of proteins represent by

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Speaker 1: the letters G, A, T, and C may differ by

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Speaker 1: only one letter. Those genes turn out to be the

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Speaker 1: ones that have spread all over the planet, showing that

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Speaker 1: many of the gene variations that cause light skin color

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Speaker 1: in Europeans actually originated in Africa. The ubiquitous nature of

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Speaker 1: skin color genes and their persistence over thousands of years

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Speaker 1: makes racial divisions seem pretty much meaningless from a biological viewpoint.

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Speaker 1: Tishkov said, I think that work strengthens what so many

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Speaker 1: geneticists and sociologists already know that race cannot be defined

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Speaker 1: based on genetic criteria. There have been many abuses committed

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Speaker 1: in the past and in the present based on that assumption,

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Speaker 1: so hopefully this and other studies will help dispel the

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Speaker 1: notion of genetically defined racial groups due to genetic variants

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Speaker 1: shared among populations around the world. The new data also

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Speaker 1: shines a light on human evolution, supporting the notion of

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Speaker 1: an early history migration of biologically modern humans out of

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Speaker 1: Africa following the southern coast of Asia into Australo Melanesia,

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Speaker 1: plus a secondary migration into other regions. Tishkov to build

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Speaker 1: upon the study and explore other questions that remain about

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Speaker 1: the genetics of skin color, she said in her email.

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Speaker 1: We want to better understand the biological mechanisms by which

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Speaker 1: these variants are impacting skin pigmentation. Our study has implications

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Speaker 1: for better understanding skin pigmentation disorders and melanoma risk. We're

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Speaker 1: also looking at the genetic basis of other adaptive traits,

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Speaker 1: as well as genetic and environmental factors influencing disease risk

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Speaker 1: in ethnically diverse African populations. Today's episode was written by

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Speaker 1: Patrick J. Keiger and produced by Tristan McNeil. For more

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Speaker 1: on this and the lots of other evolutionary topics, visit

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Speaker 1: our home planet, as to works dot com.