Mixed Race Studies

Examining Population Stratification via Individual Ancestry Estimates versus Self-Reported Race

Cancer Epidemiology, Biomarkers & Prevention
Volume 14, Issue 6 (June 2005)
pages 1545-1551
DOI: 10.1158/1055-9965.EPI-04-0832

Jill S. Barnholtz-Sloan
Cancer Prevention and Control Program
H. Lee Moffitt Cancer Center and Research Institute

Ranajit Chakraborty
Center for Genome Research, Department of Environmental Health
University of Cincinnati, Cincinnati, Ohio

Thomas A. Sellers
Cancer Prevention and Control Program
H. Lee Moffitt Cancer Center and Research Institute

Ann G. Schwartz
Population Studies and Prevention Program, Karmanos Cancer Institute and Department of Internal Medicine
Wayne State University School of Medicine, Detroit, Michigan

Population stratification has the potential to affect the results of genetic marker studies. Estimating individual ancestry provides a continuous measure to assess population structure in case-control studies of complex disease, instead of using self-reported racial groups. We estimate individual ancestry using the Federal Bureau of Investigation CODIS Core short tandem repeat set of 13 loci using two different analysis methods in a case-control study of early-onset lung cancer. Individual ancestry proportions were estimated for “European” and “West African” groups using published allele frequencies. The majority of Caucasian, non-Hispanics had >50% European ancestry, whereas the majority of African Americans had <20% European ancestry, regardless of ancestry estimation method, although significant overlap by self-reported race and ancestry also existed. When we further investigated the effect of ancestry and self-reported race on the frequency of a lung cancer risk genotype, we found that the frequency of the GSTM1 null genotype varies by individual European ancestry and case-control status within self-reported race (particularly for African Americans). Genetic risk models showed that adjusting for individual European ancestry provided a better fit to the data compared with the model with no group adjustment or adjustment for self-reported race. This study suggests that significant population substructure differences exist that self-reported race alone does not capture and that individual ancestry may be confounded with disease status and/or a candidate gene risk genotype.

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Understanding Racial-ethnic Disparities in Health: Sociological Contributions

Journal of Health and Social Behavior
Volume 51, Number 1 Supplement (November, 2010)
pages S15-S27
DOI: 10.1177/0022146510383838

David R. Williams
Harvard University

Michelle Sternthal
Harvard University

This article provides an overview of the contribution of sociologists to the study of racial and ethnic inequalities in health in the United States. It argues that sociologists have made four principal contributions. First, they have challenged and problematized the biological understanding of race. Second, they have emphasized the primacy of social structure and context as determinants of racial differences in disease. Third, they have contributed to our understanding of the multiple ways in which racism affects health. Finally, sociologists have enhanced our understanding of the ways in which migration history and status can affect health. Sociological insights on racial disparities in health have important implications for the development of effective approaches to improve health and reduce health inequities.

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Self-Reported Race and Genetic Admixture

The New England Journal of Medicine
Number 354, Number 4 (2006-01-26)
pages 431-422
DOI: 10.1056/NEJMc052515

Moumita Sinha, M.Stat.
Case Western Reserve University, Cleveland, Ohio

Emma K. Larkin, M.H.S.
Case Western Reserve University, Cleveland, Ohio

Robert C. Elston, Ph.D.
Case Western Reserve University, Cleveland, Ohio

Susan Redline, M.D., M.P.H.
Case Western Reserve University, Cleveland, Ohio

To the Editor:

The use of data on self-reported race in health research has been highly debated. For example, Burchard et al. recently argued that important information on disease susceptibility may be derived from the use of data on self-reported race, whereas Cooper et al. cited Wilson et al., who argued that ethnic labels “are inaccurate representations of the inferred genetic clusters.” Cooper et al., however, ignored later work that identified limitations in the analyses of Wilson et al. — specifically, inappropriate classification of groups, the use of a suboptimal model for cluster identification, and reliance on only 39 microsatellite markers for cluster analyses. With larger numbers of markers, it was shown that genetically distinct groups can be almost completely inferred from self-reported race…

…With support from a U.S. Public Health Service grant, we applied an admixture analysis to a sample population in Cleveland. Participants were clearly separated into unique groups with the use of this genetic approach. Whereas 93 percent of self-reported whites were classified as having predominantly European ancestry, less than 2 percent of blacks were so classified. Only 4 percent who reported their race as black had predominantly African ancestry; yet, the admixture proportions of this group made it possible to separate the population into two groups, in which 94 percent of self-reported blacks and 7 percent of self-reported whites were classified as being of mixed race (Figure 1: Frequency Histogram Showing the Percentage of African Ancestry in a Population Living in Cleveland). The sharp peak at the left in Figure 1 indicates that there are many persons who have no African ancestry (i.e., the values correspond to those of self-reported whites), and the broad peak at the right indicates that most blacks are of mixed race and do not originate from any single population. Thus, self-reported race and genetic ethnic ancestry appear to be highly correlated as a dichotomy, with those who self-report as being black comprising, as expected from historical and cultural practices in the United States, a broad range of African ancestry…

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Comparing Genetic Ancestry and Self-Described Race in African Americans Born in the United States and in Africa

Cancer Epidemiology, Biomarkers & Prevention
Volume 17, Issue 6 (June 2008)
pages 1329-1338
DOI: 10.1158/1055-9965.EPI-07-2505

Rona Yaeger
Herbert Irving Comprehensive Cancer Center

Alexa Avila-Bront
Department of Medicine
College of Physicians and Surgeons of Columbia University

Kazeem Abdul
Herbert Irving Comprehensive Cancer Center

Patricia C. Nolan
Department of Medicine
College of Physicians and Surgeons of Columbia University

Victor R. Grann
Department of Medicine
College of Physicians and Surgeons of Columbia University

Mark G. Birchette
Department of Biology
Long Island University, Brooklyn, New York

Shweta Choudhry
Department of Biopharmaceutical Sciences and Medicine
University of California-San Francisco, San Francisco, California

Esteban G. Burchard
Department of Biopharmaceutical Sciences and Medicine
University of California-San Francisco, San Francisco, California
 
Kenneth B. Beckman
Children’s Hospital Oakland Research Institute, Oakland, California

Prakash Gorroochurn
Department of Biostatistics
Columbia University Medical Center, New York, New York

Elad Ziv
Division of General Internal Medicine
University of California-San Francisco, San Francisco, California

Nathan S. Consedine
Department of Psychology
Long Island University, Brooklyn, New York

Andrew K. Joe
Herbert Irving Comprehensive Cancer Center

Genetic association studies can be used to identify factors that may contribute to disparities in disease evident across different racial and ethnic populations. However, such studies may not account for potential confounding if study populations are genetically heterogeneous. Racial and ethnic classifications have been used as proxies for genetic relatedness. We investigated genetic admixture and developed a questionnaire to explore variables used in constructing racial identity in two cohorts: 50 African Americans and 40 Nigerians. Genetic ancestry was determined by genotyping 107 ancestry informative markers. Ancestry estimates calculated with maximum likelihood estimation were compared with population stratification detected with principal components analysis. Ancestry was approximately 95% west African, 4% European, and 1% Native American in the Nigerian cohort and 83% west African, 15% European, and 2% Native American in the African American cohort. Therefore, self-identification as African American agreed well with inferred west African ancestry. However, the cohorts differed significantly in mean percentage west African and European ancestries (P < 0.0001) and in the variance for individual ancestry (P ≤ 0.01). Among African Americans, no set of questionnaire items effectively estimated degree of west African ancestry, and self-report of a high degree of African ancestry in a three-generation family tree did not accurately predict degree of African ancestry. Our findings suggest that self-reported race and ancestry can predict ancestral clusters but do not reveal the extent of admixture. Genetic classifications of ancestry may provide a more objective and accurate method of defining homogenous populations for the investigation of specific population-disease associations.

Introduction

Genome-wide case-control association studies provide a powerful tool for investigating possible genetic factors that may contribute to the health disparities observed among different racial and ethnic populations. Populations with different ancestral backgrounds may carry different genetic variants, and these may contribute to the variations in disease incidence and outcomes seen in specific racial and ethnic groups (1). Association studies can most easily identify disease-associated alleles when study groups are genetically similar, sharing a similar ancestral background (2). However, individual ancestry is not an easily assayed, simple category; consequently, race continues to be used as a proxy for genetic relatedness in clinical and other biological studies (3-6). There is currently no consensus on how best to examine or characterize different racial or ethnic groups when designing and conducting such studies.

Two main approaches have been used to approximate individual ancestry in biological studies: (a) using self identified race and ethnicity, which may capture common environmental influences as well as ancestral background, and (b) genotyping a panel of markers that show large frequency differentials between major geographic ancestral groupings (7, 8). Both approaches have limitations. Self-identified racial categories may not always consistently predict ancestral population clusters, and evidence suggests that it may take large sample sizes and numerous markers to describe genetic clusters that correspond to self-identified race and ethnicity groupings (9-11). Racial categories are also imprecise and inconsistent, because they may potentially vary within the same individual over time (12, 13). Furthermore, their use risks reinforcing racial divisions in society. On the other hand, more objective analyses that genotype markers that are highly informative for ancestry may not be economically practical and are limited by the requirement of serum or fresh tissue for DNA extraction. Genetically determined ancestry may not capture unmeasured social factors that may affect differences in health outcomes. There are also unique ethical challenges when linking biological phenotypes with genetic markers for specific racial groups, and caution must always be used when attributing biological differences (e.g., disease risk and treatment response) to different populations.

Understanding the ancestral background of study subjects is most important in genetic studies of admixed populations, such as African Americans, who represent an admixture of Africans, Europeans, and Native Americans (14). Genetic studies have shown that African Americans form a diverse group with percent European admixture estimated to range between 7% and 23% (14-16). Genotyping of self-identified African Americans participating in the Cardiovascular Health Study revealed that among self-reported Africans there are differences in genetic ancestry that are correlated with some clinically important endpoints (15).

…Discussion…

The African American cohort in our study had a mean of 15% European admixture, which is consistent with previous reports of a range of 7% to 23% European admixture among U.S. African Americans (14-16). Of note, the estimates of 4% European and 1% Native American ancestry in the Nigerian population is likely due to bias in MLE due to the limited number of markers. We found that among participants there was a significantly higher proportion of admixture and higher variability in admixture proportions in the U.S.-born African American cohort compared with a population that emigrated from Africa (that is, Nigerians; Table 3). The significant variation in individual ancestry estimates among the African American cohort suggests that this group, like the Cardiovascular Health Study African American cohort (15), represents a diverse population consisting of several subpopulations. For participation in the African American cohort, subjects identified both parents as African Americans who were born in the United States. Although data regarding grandparental race were not used to screen study participation, these data were collected through a three-generation family tree during administration of the questionnaire. In this study population, all African American subjects described that the race of at least three of their four grandparents was consistent with African ancestry. Individuals and society have historically classified children of mixed-race ancestry as African American, even when one parent is Caucasian, Asian, or Native American. For African Americans, this is a remnant of the ‘‘Jim Crow’’ laws and the ‘‘One Drop’’ rule or ‘‘Rule of Hypodescent.’’ Thus, identification as African American would still occur in cases where the parents and grandparents were of mixed-race ancestry. This could also contribute to the greater European admixture and greater admixture variability seen in the African American cohort…

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Lansing has highest percentage of people who identify as multiple-race black

Lansing State Journal
2011-11-18

Matthew Miller

Gianni Risper has a black mother, a white biological father (as opposed to the father who raised him, his mother’s husband) and a way of describing himself that isn’t found on any Census form: Italian-Caribbean-American.

“Race is becoming more muddled,” he said, and, at 19, he is part of a generation that is muddling it, more likely to be mixed race than their elders, more likely to reject the rigidity of prevailing racial categories in favor of more fluid identities.

“I try not to put myself into a category of being either black or white or just one thing,” Risper said, “because I’m not.”

And, living in Lansing, he has plenty of company.

Lansing has the highest percentage of people who identify as black and some other race of any place in the country, at least any place with a population of 100,000 or more.

According to the 2010 Census, it’s 4.1 percent, more than one out of every 25 people in the city…

…Kristen Renn, a professor of education at Michigan State University who has studied mixed-race identity in college students, said space began to open up for more complicated racial identities in the latter part of the 1990s.

“Part of this is liberal baby boomers marrying outside their race or having kids with people of other races and liberal baby boomers being very vested in raising happy children,” she said.

But the shift also coincided with the growth of the Internet, which made it easier to create communities around mixed-race identities or even specific racial combinations.

It coincided with celebrities – Renn mentioned Tiger Woods – beginning to speak publicly about their blended ancestries.

As a result, among the younger generation in particular, “it has become more OK,” she said. “There is a youth movement around mixed race.”

And if that’s more true in Lansing than other places, she sees it as a good sign.

“When people are less comfortable, they have to draw the boundaries much more clearly, ‘You’re one of them. You’re one of us. You’ve got to be one or the other,’ ” she said.

“People in more cosmopolitan areas are just used to a more diverse, global kind of population.”…

…Self-definition

Nikki O’Brien was raised by her white mother. She didn’t know her black father until she was an adult. She identifies herself as black.

“You’d think I would be more malleable in my racial identity,” she said, “but really the experience of being other or different was enough that I constantly knew that I was black and the strength and community that I pulled from that identity just pushed me.”

But O’Brien, a program adviser at MSU who spent years working with minority students, sees the conversation about mixed-race identity more as one about self-definition, including the right to identify as one race or another…

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Mixed-race Koreans urge identity rethink

The Korea Herald
2011-12-07

Kirsty Taylor

Things have come a long way since the 1970s when mixed-race Koreans here were spat upon and beaten up for being different.

The kids of that time, whose fathers were often foreign soldiers who first came here during the Korean War, used to find it hard to walk down the street for fear of discrimination.

These days, the Korean government and charities are investing heavily in programs to support multicultural families and overt discrimination against Amerasians is rare.

But African-American Korean Yang Chan-wook, who goes by his Korean name here rather than his western name of Gregory Diggs, said that small daily occurrences remind him that this society does not yet fully accept him.

“In the 1970s these kids could not go to school, but even now, mixed-race Koreans going into public schools have a pretty high dropout rate,” he said.

“Sometimes when I am on the bus people will look at me and if they think that I am not Korean they will not sit next to me or they will move when I sit down. This kind of thing is still existent. Also, it can be difficult to get people to stop speaking English with me. Even if I have been speaking in Korean with them for 20 minutes they will still try to speak in English as if they thought I could not understand…

…After living with this prejudice, Yang started the M.A.C.K. Foundation (Movement for the Advancement of the Cultural diversity of Koreans) upon returning in 2003, basing it on a similar mission started in Chicago in 1995…

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Dominican Republic Country Profile

BBC News
2011-12-06

Once ruled by Spain, the Dominican Republic shares the island of Hispaniola with Haiti, a former French colony.

OVERVIEW…

…The Dominican Republic is inhabited mostly by people of mixed European and African origins. Western influence is seen in the colonial buildings of the capital, Santo Domingo, as well as in art and literature. African heritage is reflected in music. The two heritages blend in the popular song and dance, the merengue.

No blending of fortunes, however, is evident in the distribution of wealth between ethnic groups.

The Dominican Republic is one of the poorest countries in the Caribbean. There is a huge gap between the rich and the poor, with the richest being the white descendants of Spanish settlers, who own most of the land, and the poorest comprising people of African descent. The mixed race majority controls much of the commerce. …

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The Measurement of Negro “Passing”

American Journal of Sociology
Volume 52, Number 1 (July, 1946)
pages 18-22

John H. Burma

Older and popular methods of estimating the number of Negroes who pass over into the white group are no longer to be credited. Considerable misconception exists concerning passing itself, which is more frequently temporary and opportunistic than permanent and complete. In the absence of scientifically accurate counts, the lower estimates of passing are probably more reliable.

Whenever a minority group is oppressed or is the subject of discrimination, some individual members attempt to escape by losing their identity with the minority and becoming absorbed into the majority. In the United States the Negro is such a minority group. In many cases a foreigner may become indistinguishable in a country by adopting the language, customs, and dress of that country. This technique, of

TABLE 1: native whites of native parentage, by Age Groups, for 1900 and 1910

Ages		Populations		Increase or Descrease
1900	1910	1900	1910
0-4…	10-14	5,464,881	5,324,283	-140,589
5-9…	15-19	5,174,220	5,089,055	-85,165
10-14…	20-24	4,660,390	4,682,922	+22,532
15-19…	25-29	4,234,953	4,049,074	-185,879
20-24…	30-34	3,805,609	3,401,601	-404,008

course, avails the Negro little because of his high visibility.

Being a Negro in America is not just a biological matter, it is a legal and social matter as well. It has been declared, by law, how much Negro heredity makes one a Negro; and because of the determination to prevent the infusion of Negro blood into the white group, the law frequently decreed that a person of one thirty-second, one sixty-fourth, or “any discernible amount” of Negro blood was a Negro. This meant that many persons who were legally Negro had so much white blood that they were, biologically, indistinguishable from whites. This, in turn, led to a considerable number of “white Negroes” being mistaken for legal whites and being treated as such. Some of this group, we have long been aware, simply went where they were not personally known and became a permanent part of the white group.

This passing of the legal Negro for white has been well known for over one hundred and fifty years. What we have not been able to ascertain accurately was the number of these legal Negroes who passed as white. This lack of concrete knowledge did not, of course, prevent considerable speculation and opinionated estimates. By the very secrecy which must involve passing, its investigation is almost insuperably hindered, and seldom, if ever, have estimates agreed.

The first, and by far the most widely known, effort to arrive at an unbiased estimate of the number of legal Negroes who have more or less permanently passed into the white group was made by Hornell Hart rather incidentally to a study of migration. His method of analysis was a breakdown of the census returns for native whites of native parentage, by age groups. The reasoning involved hinges on the fact that this group cannot increase. Emigration might logically decrease it, as would deaths, but there should be no increases. Yet, as is seen by Table 1, Hart found a marked increase. In fact, the group who had been between…

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Patterns of gene flow between Negroes and whites in the US

Journal of Biosocial Science
Volume 8, Issue 4 (1976)
pages 309-333
DOI: 10.1017/S002193200001083X

K. F. Dyer
Department of Genetics
University of Adelaide, South Australia

A review of the pattern and magnitude of negro–white mating in the US is presented from the time of the earliest arrival of negroes in the American colonies until the present, using historical, demographic, census and genetic evidence.

The relative magnitude of negro male–white female matings compared to the converse are analysed in view of the different genetic outcomes of these two types of mating for X-linked genes. Contrary to many strongly stated opinions it is conclued from the historical evidence that, even from the earliest days of slavery, negro male–white female matings were a significant proportion of all negro–white matings. Census and demographic evidence suggests that their frequency increased so that from the time of the Civil War on they have formed a majority of inter-racial matings.

Genetic evidence based on estimates of the amout of admixture of white genes in a number of negro populations is considered. Estimates of admixture for the X-linked genes G6PD, and those for colour blindness are as high or higher than those derived from comparable autosomal genes.

Some observations on the total magnitude of negro–white mating, on the phenomenon of passing and on the relative socio-economic status of those involved are also made.

The implication of the findings on these phenomena for investigations and hypotheses concerning differences in intelligence and intellectual abilites between the races, particulary spatial ability which is thought to be strongly influenced by a gene on the X chromosome, are considered.

It is concluded that some of the assumptions made in proposing hypotheses regarding the origin and distribution of these abilities in the American negro are at variance with genetic, historical and sociological findings.

Washed in the Blood

Mercer University Press
October 2011
420 pages
Hardback ISBN: 9780881462579

Lisa Alther

This unique three-part novel assumes that, regardless of what Americans learn in school, the Southeast was not a barren wilderness when the English arrived at Jamestown. It was full of Native Americans, other Europeans, and Africans who were there for various reasons. Based on extensive research into the racial mixing that occurred in the early years of southeastern settlement, this provocative multi-generational story shows that these people did not simply vanish, but that many were absorbed into the new communities that gradually formed throughout the southeast, becoming “white” whenever their complexions allowed. The inability to accept their true heritages illustrates the high price many of these people paid for their way of life. Diego Martin arrives in 1567 in the American Southeast—the region the Spaniards call La Florida—as a hog drover with a Spanish exploring party. The leader of the expedition turns against him and abandons him to the wilderness, where friendly natives rescue him. Daniel Hunter, a Quaker from Philadelphia, sets up a school among these “disadvantaged” mountain people and falls in love with a Martin daughter. Later, Daniel’s descendants are living in the same town, though with little awareness of their ancestral past. The Martin family has split in two, the merchants in town denying any relationship to their racially mixed cousins on Mulatto Bald. A young woman from town, Galicia, falls in love with a young man from the bald, Will, not realizing that he is her cousin. They marry, have a daughter, and move to a new industrial center, becoming prominent citizens. When Will’s son from a teenage liaison appears at his door, he invites him in, unwittingly setting the stage for a forbidden love between his unacknowledged son and his cherished daughter, neither of whom realizes that they are half-siblings. This is a novel you will not be able to put down without wondering “Where will it take me next?”

Table of Contents

• Part I – The Swine King: A. D. 1567
  • 1-The San Jorge
  • 2 – Landfall
  • 3 – Santo Domingo
  • 4 – Santa Elena
  • 5 – Orista
  • 6 – Cofitachequi
  • 7 – Joara
  • 8 – Cauchi
  • 9 – Land of the Lost
  • 10 – The Cave
• Part II – The Squabble State
  • 1 – The Five-Chicken Baby: 1818
  • 2 – Couchtown: August 1837
  • 3 – The Shenandoah: October 1837
  • 4 – Mulatto Bald: October 1837
  • 5 – Baptism by Fire: November 1837
  • 6 – The Frost Moon: December 1837
  • 7 – Seedbeds: April 1838
  • 8 – Soldiers’Joy: June 1838
  • 9 – The Wilderness Road: July 1838
  • 10 – Squatters: October 1838
• Part III – Passing Fancy
  • 1 – The Ringer: August 1909
  • 2 – Leesville: October 1909
  • 3 – Palestine: February 1911
  • 4 – Hijacked Happiness: March 1911
  • 5 – Old Times There Are Not Forgotten: April 1911
  • 6 – Homecoming: December 1911
  • 7 – Mongrels: August 1913
  • 8 – A Roll of the Dice: November 1913
  • 9 – The Perils of Pauline: March 1914
  • 10 – Holston: May 1914
  • 11 – Half-Breeds: 1920
  • 12 – Home to Roost: 1927
  • 13 – Mountain Meadows: 1930
  • 14 – The Plantation Ball: 1930