Mixed Race Studies

Large DNA Study Traces Violent History of American Slavery

The New York Times
2020-07-23

Christine Kenneally

An 1823 cross-section diagram of a ship used to carry enslaved people. incamerastock/Alamy

Scientists from the consumer genetics company 23andMe have published the largest DNA study to date of people with African ancestry in the Americas.

More than one and a half centuries after the trans-Atlantic slave trade ended, a new study shows how the brutal treatment of enslaved people has shaped the DNA of their descendants.

The report, which included more than 50,000 people, 30,000 of them with African ancestry, agrees with the historical record about where people were taken from in Africa, and where they were enslaved in the Americas. But it also found some surprises.

For example, the DNA of participants from the United States showed a significant amount of Nigerian ancestry — an unexpected finding, as the historical record does not show evidence of enslaved people taken directly to the United States from Nigeria.

At first, historians working with the researchers “couldn’t believe the amount of Nigerian ancestry in the U.S.,” said Steven Micheletti, a population geneticist at 23andMe who led the study…

…The 23andMe project found this general pattern, but also uncovered a startling difference in the experience of men and women between regions in the Americas.

The scientists calculated that enslaved women in the United States contributed 1.5 times more to the modern-day gene pool of people of African descent than enslaved men. In the Latin Caribbean, they contributed 13 times more. In Northern South America, they contributed 17 times more.

What’s more, in the United States, European men contributed three times more to the modern-day gene pool of people of African descent than European women did. In the British Caribbean, they contributed 25 times more…

Read the entire article here.

Genetic Consequences of the Transatlantic Slave Trade in the Americas

The American Journal of Human Genetics
Published: 2020-07-23
37 pages
DOI:10.1016/j.ajhg.2020.06.012

Steven J. Micheletti
23andMe, Inc., Sunnyvale, California

Kasia Bryc
23andMe, Inc., Sunnyvale, California

Samantha G. Ancona Esselmann
23andMe, Inc., Sunnyvale, California

William A. Freyman
23andMe, Inc., Sunnyvale, California

Meghan E. Moreno
23andMe, Inc., Sunnyvale, California

G. David Poznik
23andMe, Inc., Sunnyvale, California

Anjali J. Shastri
23andMe, Inc., Sunnyvale, California

23andMe Research Team
23andMe, Inc., Sunnyvale, California

Sandra Beleza
University of Leicester, Leicester, United Kingdom

Joanna L. Mountain
23andMe, Inc., Sunnyvale, California

GettyImages

According to historical records of transatlantic slavery, traders forcibly deported an estimated 12.5 million people from ports along the Atlantic coastline of Africa between the 16th and 19th centuries, with global impacts reaching to the present day, more than a century and a half after slavery’s abolition. Such records have fueled a broad understanding of the forced migration from Africa to the Americas yet remain underexplored in concert with genetic data. Here, we analyzed genotype array data from 50,281 research participants, which—combined with historical shipping documents—illustrate that the current genetic landscape of the Americas is largely concordant with expectations derived from documentation of slave voyages. For instance, genetic connections between people in slave trading regions of Africa and disembarkation regions of the Americas generally mirror the proportion of individuals forcibly moved between those regions. While some discordances can be explained by additional records of deportations within the Americas, other discordances yield insights into variable survival rates and timing of arrival of enslaved people from specific regions of Africa. Furthermore, the greater contribution of African women to the gene pool compared to African men varies across the Americas, consistent with literature documenting regional differences in slavery practices. This investigation of the transatlantic slave trade, which is broad in scope in terms of both datasets and analyses, establishes genetic links between individuals in the Americas and populations across Atlantic Africa, yielding a more comprehensive understanding of the African roots of peoples of the Americas.

Figure 1 Location of Individuals and Cohorts Arrows highlight the general direction of the triangular trade routes between continents during the transatlantic slave trade. Pie charts indicate the documented number of enslaved people embarking out of regions of Africa (∼12.5 million total) and disembarking in regions of the Americas (∼10.5 million total) between 1515 and 1865. Representatives of regions of the Americas and Europe indicated that they each have four grandparents born within the same country or US state. Representatives of Atlantic Africa either indicated four grandparents born within or historical ties to a country. Points indicate the ∼16,000 unique grandparental geo-coordinates provided by participants. ∗Cape Verde is an Atlantic African island country that, in the 15th century, was colonized by the Portuguese and inhabited primarily by enslaved people from Senegambia.

Read the entire article in HTML or PDF format.

White? Black? A Murky Distinction Grows Still Murkier

The New York Times
2014-12-24

Carl Zimmer

In 1924, the State of Virginia attempted to define what it means to be white.

The state’s Racial Integrity Act, which barred marriages between whites and people of other races, defined whites as people “whose blood is entirely white, having no known, demonstrable or ascertainable admixture of the blood of another race.”

There was just one problem. As originally written, the law would have classified many of Virginia’s most prominent families as not white, because they claimed to be descended from Pocahontas.

So the Virginia legislature revised the act, establishing what came to be known as the “Pocahontas exception.” Virginians could be up to one-sixteenth Native American and still be white in the eyes of the law.

People who were one-sixteenth black, on the other hand, were still black.

In the United States, there is a long tradition of trying to draw sharp lines between ethnic groups, but our ancestry is a fluid and complex matter. In recent years geneticists have been uncovering new evidence about our shared heritage, and last week a team of scientists published the biggest genetic profile of the United States to date, based on a study of 160,000 people…

Read the entire article here.

The Genetic Ancestry of African Americans, Latinos, and European Americans across the United States

The American Journal of Human Genetics
Volume 96, Issue 1, 2015-01-08
Pages 37–53
DOI: 10.1016/j.ajhg.2014.11.010

Katarzyna Bryc, Research Fellow in Genetics (EXT)
Department of Genetics
Harvard Medical School, Boston, Massachusetts

Eric Y. Durand
23andMe, Inc., Mountain View, California

J. Michael Macpherson, Assistant Professor
School of Computational Sciences
Chapman University, Orange, California

David Reich, Professor of Genetics
Harvard Medical School, Boston, Massachusetts

Joanna L. Mountain, Senior Director of Research
23andMe, Inc., Mountain View, California

Over the past 500 years, North America has been the site of ongoing mixing of Native Americans, European settlers, and Africans (brought largely by the trans-Atlantic slave trade), shaping the early history of what became the United States. We studied the genetic ancestry of 5,269 self-described African Americans, 8,663 Latinos, and 148,789 European Americans who are 23andMe customers and show that the legacy of these historical interactions is visible in the genetic ancestry of present-day Americans. We document pervasive mixed ancestry and asymmetrical male and female ancestry contributions in all groups studied. We show that regional ancestry differences reflect historical events, such as early Spanish colonization, waves of immigration from many regions of Europe, and forced relocation of Native Americans within the US. This study sheds light on the fine-scale differences in ancestry within and across the United States and informs our understanding of the relationship between racial and ethnic identities and genetic ancestry.

Read the entire article here.

The Meanings of “Race” in the New Genomics: Implications for Health Disparities Research

Yale Journal of Health Policy, Law, and Ethics
Volume 1, Issue 1 (2001)
pages 33-76

Sandra Soo-Jin Lee, Senior Research Scholar
Stanford Center for Biomedical Ethics
Stanford University

Joanna Mountain, Assistant Professor of Anthropological Genetics
Stanford University

Barbara A. Koenig, Professor of Biomedical Ethics and of Medicine at the College of Medicine, Mayo Clinic;
Affiliate Faculty of the Center for Bioethics, University of Minnesota, Minneapolis;
Stanford Center for Biomedical Ethics, Stanford University

Eliminating the well-documented health disparities found within the United States population is a laudable public policy goal. Social justice demands that we understand the sources of health inequality in order to eliminate them. A central dilemma is: To what extent are health disparities the result of unequal distribution of resources, and thus a consequence of varied socioeconomic status (or blatant racism), and to what extent are inequities in health status the result of inherent characteristics of individuals defined as ethnically or racially different? How we conceptualize and talk about race when we ask these questions has profound moral consequences. Prior to the Human Genome Project (HGP), scientific efforts to understand the nature of biological differences were unsophisticated. The new technologies for genomic analysis will likely transform our thinking about human disease and difference, offering the promise of in-depth studies of disease incidence and its variations across human populations. In her opening remarks at a meeting of the President’s Cancer Panel, which focused on health disparities in cancer treatment in the United States, Dr. Karen Antman noted that racial differences in cancer rates have been reported for decades, “but for the first time, science now has the opportunity to quantify such differences genetically.” Will the light refracted through the prism of genomic knowledge illuminate straightforward explanations of disease etiology, offering simple solutions to health inequalities? Or are there consequences, currently hidden in the shadows, that require our attention?

The challenge is then to analyze the causes of racism while avoiding the implication that race exists.
-Steven Miles, 1993

A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines.
-Ralph Waldo Emerson, “Self-Reliance,” 1841

Eliminating the well-documented health disparities found within the United States population is a laudable public policy goal. Social justice demands that we understand the sources of health inequality in order to eliminate them. A central dilemma is: To what extent are health disparities the result of unequal distribution of resources, and thus a consequence of varied socioeconomic status (or blatant racism), and to what extent are inequities in health status the result of inherent characteristics of individuals defined as ethnically or racially different? How we conceptualize and talk about race when we ask these questions has profound moral consequences.

Prior to the Human Genome Project (HGP), scientific efforts to understand the nature of biological differences were unsophisticated. The new technologies for genomic analysis will likely transform our thinking about human disease and difference, offering the promise of in-depth studies of disease incidence and its variations across human populations. In her opening remarks at a meeting of the President’s Cancer Panel, which focused on health disparities in cancer treatment in the United States, Dr. Karen Antman noted that racial differences in cancer rates have been reported for decades, “but for the first time, science now has the opportunity to quantify such differences genetically.” Will the light refracted through the prism of genomic knowledge illuminate straightforward explanations of disease etiology, offering simple solutions to health inequalities? Or are there consequences, currently hidden in the shadows, that require our attention?…

…Increasing ability to detect genetic mutations linked to disease susceptibility has not been paralleled by therapeutic discoveries. This disjuncture has contributed to the conflict about population-based testing and disagreement about the calculus of the largely unknown risks and benefits to individuals and populations. Knowing one has a BRCA mutation does not mean that one will ultimately develop cancer. Individuals must interpret complex, uncertain information to make sense of their cancer risk, and are often confused as to how to make sense of genetic information. The additional burden of contemplating the ramifications of targeted testing of their community, including the possibility of categorical discrimination and prejudice, is a daunting challenge. The mutations found most commonly among those of Ashkenazi ancestry were identified by chance. Blood stored for other purposes, notably screening for Tay Sachs, a heritable disease, was available for research. Other mutations in the BRCA-1 and BRCA-2 genes are specific to certain groups, generally isolated populations such as those in Iceland or Finland. How will knowledge that common diseases are associated with socially identifiable populations affect the treatment of those individuals? But more importantly, how will an increasingly sophisticated knowledge of molecular genetics affect our understanding of the nature of “difference” among human groups?…

…In this paper we provide a strong critique of the continued use of race as a legitimate scientific variable. We offer an historical analysis of how the concept of race has changed in the United States and discuss the reification of race in health research. We discuss how genetic technology has been deployed in “proving” racial identity, and describe the consequences of locating human identity in the genes. The implications of the continued use of race in the new genomic medicine—in particular the creation of racialized diseases—is highlighted. We warn about the consequences of a shift toward population-based care, including targeted genetic screening for racially identified “at-risk” groups, including the potential for stigmatization and discrimination. A less commonly identified hazard is the epistemological turn towards genetic reductionism. We suggest that the application of a naive genetic determinism will not only reinforce the idea that discrete human races exist, but will divert attention from the complex environmental, behavioral, and social factors contributing to an excess burden of illness among certain segments of the diverse U.S. population. The intersection of the genomics revolution with the health disparities initiative should serve as a catalyst to a long overdue public policy debate about the appropriate use of the race concept in
biomedical research and clinical practice…

Read the entire article here.

The Importance of Race and Ethnic Background in Biomedical Research and Clinical Practice

New England Journal of Medicine
2003-03-20
Volume 348, Number 12
pages 1170-1175

Esteban González Burchard, M.D.
Elad Ziv, M.D.
Natasha Coyle, Ph.D.
Scarlett Lin Gomez, Ph.D.
Hua Tang, Ph.D.
Andrew J. Karter, Ph.D.
Joanna L. Mountain, Ph.D.
Eliseo J. Pérez-Stable, M.D.
Dean Sheppard, M.D.
Neil Risch, Ph.D.

A debate has recently arisen over the use of racial classification in medicine and biomedical research. In particular, with the completion of a rough draft of the human genome, some have suggested that racial classification may not be useful for biomedical studies, since it reflects “a fairly small number of genes that describe appearance” and “there is no basis in the genetic code for race.” In part on the basis of these conclusions, some have argued for the exclusion of racial and ethnic classification from biomedical research. In the United States, race and ethnic background have been used as cause for discrimination, prejudice, marginalization, and even subjugation. Excessive focus on racial or ethnic differences runs the risk of undervaluing the great diversity that exists among persons within groups. However, this risk needs to be weighed against the fact that in epidemiologic and clinical research, racial and ethnic categories are useful for generating and exploring hypotheses about environmental and genetic risk factors, as well as interactions between risk factors, for important medical outcomes. Erecting barriers to the collection of information such as race and ethnic background may provide protection against the aforementioned risks; however, it will simultaneously retard progress in biomedical research and limit the effectiveness of clinical decision making.

Race and Ethnic Background as Geographic and Sociocultural Constructs with Biologic Ramifications

Definitions of race and ethnic background have often been applied inconsistently. The classification scheme used in the 2000 U.S. Census, which is often used in biomedical research, includes five major groups: black or African American, white, Asian, native Hawaiian or other Pacific Islander, and American Indian or Alaska native. In general, this classification scheme emphasizes the geographic region of origin of a person’s ancestry. Ethnic background is a broader construct that takes into consideration cultural tradition, common history, religion, and often a shared genetic heritage…

…Sociocultural Correlates of Race and Ethnic Background

The racial or ethnic groups described above do not differ from each other solely in terms of genetic makeup, especially in a multiracial and multicultural society such as the United States. Socioeconomic status is strongly correlated with race and ethnic background and is a robust predictor of access to and quality of health care and education, which, in turn, may be associated with differences in the incidence of diseases and the outcomes of those diseases. For example, black Americans with end-stage renal disease are referred for renal transplantation at lower rates than white Americans. Black Americans are also referred for cardiac catheterization less frequently than white Americans. In some cases, these differences may be due to bias on the part of physicians and discriminatory practices in medicine. Nonetheless, racial or ethnic differences in the outcomes of disease sometimes persist even when discrepancies in the use of interventions known to be beneficial are considered. For example, the rate of complications from type 2 diabetes mellitus varies according to racial or ethnic category among members of the same health maintenance organization, despite uniform utilization of outpatient services and after adjustment for levels of education and income, health behavior, and clinical characteristics. The evaluation of whether genetic (as well as nongenetic) differences underlie racial disparities is appropriate in cases in which important racial and ethnic differences persist after socioeconomic status and access to care are properly taken into account…

…Racially Admixed Populations

Although studies of population genetics have clustered persons into a small number of groups corresponding roughly to five major racial categories, such classification is not completely discontinuous, because there has been intermixing among groups both over the course of history and in recent times. In particular, genetic admixture, or the presence in a population of persons with multiple races or ethnic backgrounds, is well documented in the border regions of continents and may represent genetic gradations (clines) — for example, among East Africans (e.g., Ethiopians) and some central Asian groups. In the United States, mixture among different racial groups has occurred recently, although in the 2000 U.S. Census, the majority of respondents still identified themselves as members of a single racial group. Genetic studies of black Americans have documented a range of 7 to 20 percent white admixture, depending on the geographic location of the population studied. Despite the admixture, black Americans, as a group, are still genetically similar to Africans. Hispanics, the largest and fastest growing minority population in the United States, are an admixed group that includes white and Native American ancestry, as well as African ancestry. The proportions of admixture in this group also vary according to geographic region.

Although the categorization of admixed groups poses special challenges, groups containing persons with varying levels of admixture can also be particularly useful for genetic-epidemiologic studies. For example, Williams et al. studied the association between the degree of white admixture and the incidence of type 2 diabetes mellitus among Pima Indians. They found that the self-reported degree of white admixture (reported as a percentage) was strongly correlated with protection from diabetes in this population. Furthermore, as noted above, information on race or ethnic background can provide important clues to effects of culture, access to care, and bias on the part of caregivers, even in genetically admixed populations. It is also important to recognize that many groups (e.g., most Asian groups) are highly underrepresented both in the population of the United States and in typical surveys of population genetics, relative to their global numbers. Thus, primary categories that are relevant for the current U.S. population might not be optimal for a globally derived sample…

Read the entire article here.