Mixed Race Studies

Why Is Skin Color Different? Huge Genetic Study Reveals Prevailing Theory of Pigmentation is Wrong

Newsweek
2017-11-30

Kastalia Medrano, Staff Writer

These are South African individuals in a household that exemplify the substantial skin pigmentation variability in the Khomani and Nama populations. Brenna Henn

Scientists used to think that the same small handful of genes accounted for about half of all pigment variation in human skin. A new study shows the genetic picture behind skin color is far more complex.

Research supporting the prior, simpler conclusion was skewed by Eurocentrism. Because it focused almost exclusively on Northern Eurasian populations from higher latitudes, the data missed a huge swath of the globe. Now, scientists have factored in people of color living in lower latitudes—and found that the prevailing theory is wrong.

Scientists from the Broad Institute of MIT and Harvard, Stanford University, and Stony Brook University worked with groups of indigenous southern African peoples called the KhoeSan, notable to some for their use of “click” language. They interviewed them, measured their respective heights and weights, and used a tool called a reflectometer to measure their skin pigmentation.

After seven years of research, and data gathered from about 400 individuals, the researchers realized that the closer a population lives to the equator, the greater the number of genes play a part in determining skin pigmentation. A paper describing the research was published November 30 in the scientific journal Cell.

“Previous work has shown the biomedical consequences of ethnically biased studies. Over the past 10 years, approximately 80 percent of genetic association studies were performed in European-descent groups,” Alicia Martin, a postdoctoral scientist in the lab of Broad Institute member Mark Daly, told Newsweek by email. “What we find here is that the biology of pigmentation or ‘architecture’ can be very different in Africans.” Martin says the findings emphasize the need to fund more genetic work in diverse populations…

Read the entire article here.

Loci associated with skin pigmentation identified in African populations

Science
2017-10-12
eaan8433
DOI: 10.1126/science.aan8433

Nicholas G. Crawford, Derek E. Kelly, Matthew E. B. Hansen, Marcia H. Beltrame, Shaohua Fan, Shanna L. Bowman, Ethan Jewett, Alessia Ranciaro, Simon Thompson, Yancy Lo, Susanne P. Pfeifer, Jeffrey D. Jensen, Michael C. Campbell, William Beggs, Farhad Hormozdiari, Sununguko Wata Mpoloka, Gaonyadiwe George Mokone, Thomas Nyambo, Dawit Wolde Meskel, Gurja Belay, Jake Haut, NISC Comparative Sequencing Program, Harriet Rothschild, Leonard Zon, Yi Zhou, Michael A. Kovacs, Mai Xu, Tongwu Zhang, Kevin Bishop, Jason Sinclair, Cecilia Rivas, Eugene Elliot, Jiyeon Choi, Shengchao A. Li, Belynda Hicks, Shawn Burgess, Christian Abnet, Dawn E. Watkins-Chow, Elena Oceana, Yun S. Song, Eleazar Eskin, Kevin M. Brown, Michael S. Marks, Stacie K. Loftus, William J. Pavan, Meredith Yeager, Stephen Chanock, Sarah Tishkoff

Despite the wide range of skin pigmentation in humans, little is known about its genetic basis in global populations. Examining ethnically diverse African genomes, we identify variants in or near SLC24A5, MFSD12, DDB1, TMEM138, OCA2 and HERC2 that are significantly associated with skin pigmentation. Genetic evidence indicates that the light pigmentation variant at SLC24A5 was introduced into East Africa by gene flow from non-Africans. At all other loci, variants associated with dark pigmentation in Africans are identical by descent in southern Asian and Australo-Melanesian populations. Functional analyses indicate that MFSD12 encodes a lysosomal protein that affects melanogenesis in zebrafish and mice, and that mutations in melanocyte-specific regulatory regions near DDB1/TMEM138 correlate with expression of UV response genes under selection in Eurasians.

Variation in epidermal pigmentation is a striking feature of modern humans. Human pigmentation is correlated with geographic and environmental variation (Fig. 1). Populations at lower latitudes have darker pigmentation than populations at higher latitudes, suggesting that skin pigmentation is an adaptation to differing levels of ultraviolet radiation (UVR) (1). Because equatorial regions receive more UVR than temperate regions, populations from these regions (including sub-Saharan Africans, South Asians, and Australo-Melanesians) have darker pigmentation (Fig. 1), which likely mitigates the negative impact of high UVR exposure such as skin cancer and folate degradation (1). In contrast, the synthesis of vitamin D3 in response to UVR, needed to prevent rickets, may drive selection for light pigmentation at high latitudes (1).

The basal layer of human skin contains melanocytes, specialized pigment cells that harbor subcellular organelles called melanosomes in which melanin pigments are synthesized and stored and then transferred to keratinocytes (2). Melanosome morphology and content differs between melanocytes that synthesize mainly eumelanins (black-brown pigments) or pheomelanins (pigments which range from yellow to reddish-brown) (3). Variation in skin pigmentation is due to the type and quantity of melanins generated, melanosome size, and the manner in which keratinocytes sequester and degrade melanins (4).

While over 350 pigmentation genes have been identified in animal models, only a subset of these genes have been linked to normal variation in humans (5). Of these, there is limited knowledge about loci that affect pigmentation in populations with African ancestry (6, 7).

Skin pigmentation is highly variable within Africa

To identify genes affecting skin pigmentation in Africa, we used a DSM II ColorMeter to quantify light reflectance from the inner arm as a proxy for melanin levels in 2,092 ethnically and genetically diverse Africans living in Ethiopia, Tanzania, and Botswana (table S1 and figs. S1 and S2) (8). Skin pigmentation levels vary extensively among Africans, with darkest pigmentation observed in Nilo-Saharan speaking pastoralist populations in Eastern Africa and lightest pigmentation observed in San hunter-gatherer populations from southern Africa (Fig. 2 and table S1)…

Read the entire article here.

Skin pigmentation is far more genetically complex than previously thought

Broad Institute
Massachusetts Institute of Technology, Cambridge, Massachusetts
2017-11-30

David Cameron, Director of Communications/Media Relations

Credit : Brenna Henn South African individuals in a household that exemplify the substantial skin pigmentation variability in the Khomani and Nama populations. Picture taken with consent for publication.

By studying an African population underrepresented in most datasets, researchers find genetic complexity of pigmentation varies by latitude

Many studies have suggested that the genetics of skin pigmentation are simple. A small number of known genes, it is thought, account for nearly 50 percent of pigment variation. However, these studies rely on datasets that heavily favor northern Eurasian populations—those that reside mostly in higher latitude regions.

Reporting in the November 30 issue of Cell, researchers from the Broad Institute of MIT and Harvard, Stanford University, and Stony Brook University report that while skin pigmentation is nearly 100 percent heritable, it is hardly a straightforward, Mendelian trait. By working closely with the KhoeSan, a group of populations indigenous to southern Africa, the researchers have found that the genetics of skin pigmentation become progressively complex as populations reside closer to the equator, with an increasing number of genes—known and unknown—involved, each making a smaller overall contribution.

“Africa has the greatest amount of phenotypic variability in skin color, and yet it’s been underrepresented in large scale endeavors,” said Alicia Martin, a postdoctoral scientist in the lab of Broad Institute member Mark Daly. “There are some genes that are known to contribute to skin pigmentation, but by and large there are many more new genes that have not been discovered.”

“We need to spend more time focusing on these understudied populations in order to gain deeper genetic insights,” said Brenna Henn, assistant professor in the Department of Ecology and Evolution at Stony Brook University who, along with Martin, is a co-corresponding author…

Read the entire article here.

An Unexpectedly Complex Architecture for Skin Pigmentation in Africans

Cell
Volume 171, Issue 6, 2017-11-30
pages 1340–1353.e14
DOI: 10.1016/j.cell.2017.11.015

Alicia R. Martin, Meng Lin, Julie M. Granka, Justin W. Myrick, Xiaomin Liu, Alexandra Sockell, Elizabeth G. Atkinson, Cedric J. Werely, Marlo Möller, Manjinder S. Sandhu, David M. Kingsley, Eileen G. Hoal, Xiao Liu, Mark J. Daly, Marcus W. Feldman, Christopher R. Gignoux, Carlos D. Bustamante, Brenna M. Henn

Highlights

• Skin pigmentation in Africans is far more polygenic than light skin in Eurasians
• Southern African KhoeSan populations have lighter skin compared to equatorial Africans
• Highly heritable KhoeSan skin color variation is poorly explained by known genes
• The study of African skin color identifies novel and canonical pigmentation genes

Approximately 15 genes have been directly associated with skin pigmentation variation in humans, leading to its characterization as a relatively simple trait. However, by assembling a global survey of quantitative skin pigmentation phenotypes, we demonstrate that pigmentation is more complex than previously assumed, with genetic architecture varying by latitude. We investigate polygenicity in the KhoeSan populations indigenous to southern Africa who have considerably lighter skin than equatorial Africans. We demonstrate that skin pigmentation is highly heritable, but known pigmentation loci explain only a small fraction of the variance. Rather, baseline skin pigmentation is a complex, polygenic trait in the KhoeSan. Despite this, we identify canonical and non-canonical skin pigmentation loci, including near SLC24A5, TYRP1, SMARCA2/VLDLR, and SNX13, using a genome-wide association approach complemented by targeted resequencing. By considering diverse, under-studied African populations, we show how the architecture of skin pigmentation can vary across humans subject to different local evolutionary pressures.

Read or purchase the article here.

Measuring the health patterns of the ‘mixed/multiple’ ethnic group in Britain: data quality problems, reporting issues, and implications for policy

International Journal of Social Research Methodology
Published online: 2017-11-25
pages 1-13
DOI: 10.1080/13645579.2017.1399623

Peter J. Aspinall, Emeritus Reader in Population Health
Centre for Health Services Studies
University of Kent, Canterbury, United Kingdom

The ‘mixed’ group, officially recognised in the 2001 Census, is one of the most rapidly growing ethnic groups in Britain. Although ‘mixed’ categorisation was added to ethnic coding in NHS datasets, our knowledge of health patterns for this population is meagre. Data quality problems remain a key obstacle, including poor reproducibility of the data and constraints on reporting due to sparse data bias. The consequent minimal and indicative evidence base has focused mainly on risky health behaviours, mental health and generic measures of self-rated health, as it has in the U.S.A. and Canada. There is negligible information on the main underlying causes of death, such as neoplasms, heart disease and stroke. Consideration should be given to pooling data across multiple years of health and general purpose surveys to enable reporting for the four ‘mixed’ categories and adjustment for mediating factors and relevant confounders, such as measures of socio-economic status.

Read or purchase the article here.

Myth of race still embedded in scientific research, scholar says

Cornell Chronicle
2017-11-20

Susan Kelley
Telephone: 607-255-9737

Dorothy Roberts, professor of law, Africana studies and sociology at the University of Pennsylvania, speaks Nov. 15 in Klarman Hall. Chris Kitchen/University Photography

The concept of “race” – the idea that humans are naturally divided into biologically distinct groups – has been definitively proven false. But the 21st century has seen a disturbing increase in scientists inaccurately presenting race as the reason for racial inequality, says an acclaimed scholar of race, gender and law.

“Social scientists absolutely should engage with this rise of racial science to work on research designs that account for structural racism and state violence and that confront the racial politics of science … and unabashedly put racial justice at the center,” said Dorothy Roberts Nov. 15.

Roberts, a professor of professor of law, Africana studies and sociology at the University of Pennsylvania, spoke on “Racism and the New Racial Science” at the 2017 Institute for the Social Sciences’ Annual Lecture in Klarman Hall.

There has been a long legacy of scientists presenting the concept of biological race as an explanation for racial inequality, Roberts said. European typologists created the idea of race in the 17th century to support slavery, colonialism and the conquest of people whom they defined as separate and inferior, Roberts said…

Read the entire article here.

‘Always remember: You’re a Madison’

The Washington Post
2017-11-14

Krissah Thompson, Feature Writer

At Montpelier, four women with ties to the estate pose with the saliva vials they used to test their DNA. From left, Mary Alexander, descended from Madison’s slave Paul Jennings; Bettye Kearse; Conny Graft, descended from Madison’s sister; and Leontyne Peck. (Eduardo Montes-Bradley/Montpelier Foundation)

Oral history said she was descended from a president and an enslaved woman. But what would her DNA say?

ORANGE, Va. — In her mind’s eye, Bettye Kearse could see her ancestor walking the worn path that led from the big house to the slave quarters.

She thought of that path each time she pulled up the long, winding driveway leading to Montpelier, the rural Virginia plantation that was once home to President James Madison.

“The first time I came here was in 1992, and the moment I actually got on the grounds I felt I belonged,” said Kearse, a retired pediatrician who lives in the Boston area.

As an African American descendant of slaves, her feelings about the Founding Father, as a man and a historical figure, are decidedly ambivalent. But she has come to love his home. From the time she was a child, her mother had told her the family’s known history began on Madison’s property — and that they were, in fact, descendants of the president and an enslaved cook named Coreen. During each of her visits to Montpelier, Kearse felt the weight of her mother’s daunting request that she carry their story through oral history, following in the West African tradition of griots, or storytellers…

James Madison, 4th president of the United States created 1835. (Library of Congress)

…In 1834, two years before James Madison died, Betsey was purchased in Tennessee as a “companion” for Emanuel — the first documented reference to Kearse’s fore­father and foremother. In 1848, a slave owner named Jeptha Billingsley brought Emanuel and Betsey to Central Texas. They apparently had the last name Madison before emancipation.

All that Kearse’s generation knows about the couple comes from the bill of sale and details in Billingsley’s will. Betsey was a “light mulatto complexion Negro woman,” born around 1815. Emanuel was “a Negro man of dark complexion,” somewhere between six and 10 years Betsey’s senior. They had at least 11 children. Nine lived to adulthood…

Read the entire article here.

The Matrix of Race: Social Construction, Intersectionality, and Inequality

SAGE Publishing
October 2017
480 pages
ISBN-13: 978-1452202693

Rodney D. Coates, Professor of Global and Intercultural Studies
Miami University, Oxford, Ohio

Abby L. Ferber, Professor of Sociology
University of Colorado, Colorado Springs

David L. Brunsma, Professor of Sociology
Virginia Polytechnic Institute and State University, Blacksburg, Virginia

The Matrix of Race: Social Construction, Intersectionality, and Inequality is a textbook that makes race and racial inequality “visible” in new ways to all students in race/ethnic relations courses, regardless of their backgrounds–from minorities who have experienced the impact of race in their own lives to members of dominant groups who might believe that we now live in a “color blind” society. The “matrix” refers to a way of thinking about race that reflects the intersecting, multilayered identities of contemporary society, and the powerful social institutions that shape our understanding of race. Its goals are to help readers get beyond familiar “us vs. them” arguments that can lead to resistance and hostility; promote self-appraisal; and stimulate more productive discussions about race and racism.

Contents

• PREFACE
• ACKNOWLEDGMENTS
• ABOUT THE AUTHORS
• PART I. INTRODUCTION TO RACE AND THE SOCIAL MATRIX
  • Chapter 1. Race and the Social Construction of Difference
    • The Social Construction of Race
    • The Social Matrix of Race
    • The Operation of Racism
    • Our Stories
    • Key Terms
    • Chapter Summary
  • Chapter 2. The Shaping of a Nation: The Social Construction of Race in America
    • Race Today: Adapting and Evolving
    • Indigenous Peoples: The Americas before Columbus
    • Discovery and Encounters: The Shaping of Our Storied Past
    • The U.S. Matrix and Intersectionality— Where Do We Go from Here?
    • Key Terms
    • Chapter Summary
• PART II. THE MATRIX PERSPECTIVE ON SOCIAL INSTITUTIONS
  • Chapter 3. The Social Construction and Regulation of Families
    • Historical Regulation of the Family
    • Family Inequality Theories
    • Family Inequality through the Matrix Lens
    • Transforming the Ideal Family Narrative
    • Key Terms
    • Chapter Summary
  • Chapter 4. Work and Wealth Inequality
    • Recent Trends in Work and Wealth
    • Theories of Economic Inequality
    • Applying the Matrix to the History of Economic Inequality in the United States
    • Transforming the Story of Race and Economic Inequality
    • Key Terms
    • Chapter Summary
  • Chapter 5. Health, Medicine, and Health Care
    • Patterns of Inequality in Health and Health Care
    • Theorizing Inequality in Health and Health Care
    • Applying the Matrix to Health Inequity and Inequality
    • Resisting and Transforming Inequality in Health and Health Care
    • Key Terms
    • Chapter Summary
  • Chapter 6. Education
    • The Shaping of the Matrix of U.S. Education
    • Theories of Education
    • Examining the Concealed Story of Race and Education through the Matrix
    • Alternative Educational Movements and the Future of Education
    • Key Terms
    • Chapter Summary
  • Chapter 7. Crime, Law, and Deviance
    • A History of Race, Crime, and Punishment
    • Sociological Stock Theories of Crime and Deviance
    • Applying the Matrix to Crime and Deviance
    • Transforming the Narrative of Race, Crime, and Deviance
    • Key Terms
    • Chapter Summary
  • Chapter 8. Power, Politics, and Identities
    • Contemporary Political Identities
    • Critiquing Sociological Theories of Power, Politics, and Identity
    • Applying the Matrix of Race to U.S. Political History
    • Building Alternatives to the Matrix of Race and Politics
    • Key Terms
    • Chapter Summary
  • Chapter 9. Sports and the American Dream
    • The State of Sport Today
    • Examining Stock Sociological Theories of Sport
    • Applying the Matrix to Sports in the United States
    • Creating a New Playing Field
    • Key Terms
    • Chapter Summary
  • Chapter 10. The Military, War, and Terrorism
    • Class, Gender, and Race in the U.S. Military
    • Military Sociology Stock Theories
    • Applying the Matrix Approach to U.S. Military History, War, and Terrorism
    • A More Inclusive Future
    • Key Terms
    • Chapter Summary
  • Conclusion
• GLOSSARY
• REFERENCES
• INDEX

Woman takes 2 ancestry tests, gets 2 wildly different results

The Grio
2017-11-03

A Chicago-area woman wanted to test the accuracy of the popular DNA tests that are supposed to find your family history, but when she mailed away her DNA, the results she got were vastly different from each other.

Jennifer Smith was interested in her family ancestry, so she tried out a DNA kit from Ancestry.com, but was shocked when her breakdown showed that she was 97 percent European and 2 percent Asian.

“I’m a Black girl; I am not a Jewish white lady,” Smith told Fox32 Chicago, recalling her utter confusion at her results…

…William Gilliland, an associate biology professor at Depaul University, explained that “DNA tests for ethnicity are entertainment value only,” noting that while DNA tests can connect you to family members, there is no solid DNA marker or “diagnostic nucleotide” for race…

Read the entire article here.

Dorothy Roberts: What’s Race Got to Do with Medicine?

TED Radio Hour
National Public Radio
2017-02-10

Guy Raz, Host

About Dorothy Roberts’ TED Talk

Doctors often take a patient’s race into account when making a diagnosis—or ruling one out. Professor Dorothy Roberts says this practice is both outdated and dangerous.

About Dorothy Roberts

Dorothy Roberts is a social justice advocate and law professor at the University of Pennsylvania. She directs the program on Race, Science, and Society in the Center for Africana Studies. Roberts is the author of Fatal Invention: How Science, Politics, and Big Business Re-create Race in the Twenty-first Century.

So sometimes getting better results in medicine isn’t just about developing new technology or drugs. Sometimes getting better results is about looking at patients in a different way.

DOROTHY ROBERTS: Yes, exactly.

RAZ: This is Dorothy Roberts.

ROBERTS: Professor of Africana studies and law and sociology at the University of Pennsylvania.

RAZ: About 15 years ago, Dorothy had an experience when she was pregnant with her fourth child.

ROBERTS: I was 44 years old when I had him, and I was considered to be a high-risk, high-maternal age.

RAZ: So her doctor had her sign up for a clinical trial.

ROBERTS: That involved a genetic test.

RAZ: And one of the first questions she was asked was about her race.

ROBERTS: They just asked me to check the box. And my question is, why use race?

RAZ: In other words, why use race when it doesn’t tell us anything about our genes? Here’s Dorothy Roberts on the TED stage…

Listen to the entire interview here. Download the interview (00:09:27) here. Read the transcript here.