Mixed Race Studies

How Europeans evolved white skin

Science
2015-04-02
DOI: 10.1126/science.aab2435

Ann Gibbons, Contributing Correspondent

ST. LOUIS, MISSOURI—Most of us think of Europe as the ancestral home of white people. But a new study shows that pale skin, as well as other traits such as tallness and the ability to digest milk as adults, arrived in most of the continent relatively recently. The work, presented here last week at the 84th annual meeting of the American Association of Physical Anthropologists, offers dramatic evidence of recent evolution in Europe and shows that most modern Europeans don’t look much like those of 8000 years ago.

The origins of Europeans have come into sharp focus in the past year as researchers have sequenced the genomes of ancient populations, rather than only a few individuals. By comparing key parts of the DNA across the genomes of 83 ancient individuals from archaeological sites throughout Europe, the international team of researchers reported earlier this year that Europeans today are a mix of the blending of at least three ancient populations of hunter-gatherers and farmers who moved into Europe in separate migrations over the past 8000 years. The study revealed that a massive migration of Yamnaya herders from the steppes north of the Black Sea may have brought Indo-European languages to Europe about 4500 years ago.

Now, a new study from the same team drills down further into that remarkable data to search for genes that were under strong natural selection—including traits so favorable that they spread rapidly throughout Europe in the past 8000 years. By comparing the ancient European genomes with those of recent ones from the 1000 Genomes Project, population geneticist Iain Mathieson, a postdoc in the Harvard University lab of population geneticist David Reich, found five genes associated with changes in diet and skin pigmentation that underwent strong natural selection…

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Mexico boasts a staggering genetic diversity, study shows

Los Angeles Times
2014-06-12

Geoffrey Mohan

SHARELINES

▼ DNA offers a nuanced answer to what it means to be Mexican
▼ Ancient genetic signal survived conquest in Mexico
▼ Latino and Hispanic labels don’t do justice to Mexico’s genome

Writers, artists and historians have long pondered what it means to be Mexican. Now science has offered its answer, and it could change how medicine uses racial and ethnic categories to assess disease risk, testing and treatment..

The broadest analysis of the Mexican genome ever undertaken reveals a nation of staggering genetic diversity, where European conquest only thinly masks the ancestral DNA of Native Americans, and where some populations remain as distinct from one another as Europeans are from Chinese, according to findings published Thursday in the journal Science.

Forty researchers, who share Latino heritage as well as professional qualms over the significance of ethnic and racial categories, teamed up across borders to analyze more than 1 million variations in the building blocks of DNA. They examined more than 500 samples collected in Mexico’s remote Indian villages and polyglot cities, and from Mexican Americans in California.

“Because these populations are so rich, so genetically differentiated, you can’t just lump them all in,” said lead investigator Carlos Bustamante, a population geneticist and co-director of Stanford University’s Center for Computational, Evolutionary and Human Genomics. “You really have to embrace that diversity and think about doing medical genetic studies on a very large scale.”

To illustrate their point, the researchers compared their new genetic data with the results of lung function tests for children in Mexico City and Latinos in the San Francisco Bay Area. They discovered that pulmonary function varied in ways that were mirrored in DNA. It was as if someone with a fraction of Maya ancestry had lungs that were 10 years older than someone with a bit of northern indigenous heritage…

…Researchers not involved in the study, however, caution that correlations between disease risk and ancestry may not have much of a genetic basis at all. In many cases, they might mask socioeconomic or environmental factors — where and how you live.

The suggestion that differences in DNA are responsible for observed differences in lung capacity “is an enormous leap,” said UC Berkeley sociologist Troy Duster, who has written extensively on the intersection of race, biology and public policy.

Lundy Braun, an Africana studies professor at Brown University who studies the intersection of race and medicine, said medicine’s focus on genetics may be overshadowing other avenues of research.

“The effects of social class on lung function have been largely ignored in favor of the focus on race and ethnic difference,” she said.

Braun and Duster worry that such genomic studies may unwittingly lend legitimacy to widely discredited ideas about racial disparities.

“There is always lurking danger that this kind of research, which emphasizes the genetic structure of ethnic and racial groups, fuels the notion that the biology or genetics of those groups explains their condition,” Duster said…

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