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…

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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.

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ASHG Denounces Attempts to Link Genetics and Racial Supremacy

AJHG (American Journal of Human Genetics)
ASHG Perspective
Volume 103, Issue 5, P636
2018-10-19
DOI: 10.1016/j.ajhg.2018.10.011

The American Society of Human Genetics (ASHG) is alarmed to see a societal resurgence of groups rejecting the value of genetic diversity and using discredited or distorted genetic concepts to bolster bogus claims of white supremacy. ASHG denounces this misuse of genetics to feed racist ideologies. In public dialog, our research community should be clear about genetic knowledge related to ancestry and genomic diversity. To that end, ASHG affirms the following:…

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Black And White In America: Study Reveals Many Americans Have Mixed Race Background They Were Unaware Of

Medical Daily
New York, New York
2014-12-18

Dana Dovey, Health Journalist

Earlier this year, National Geographic made headlines with its “Changing Face of America” article. The story explained that America was becoming more comfortable with interracial relationships, and as a result, the future would be made up of a group of people with features from multiple races. A new study has challenged this hypothesis and suggested that this “mixed race future” is already here. We just never realized it.

The study, published by Cell Press, found that there is quite a large difference in the race that people identify with and what they actually are. In a recent study, researchers analyzed the DNA of more than 160,000 Americans who had offered their saliva as part of the 23andMe project. What researchers found was surprising.

The study found that, as expected, people tended to identify with the race that made up the majority of their background. However, for many, this self-identification was not completely accurate. According to the press release, the team estimated that as many as six million Americans who identify as white from a European background carry African ancestry and as many as five million self-described European white Americans have Native American ancestry….

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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.

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Gene Flow from White into Negro Populations in Brazil

American Journal of Human Genetics
Volume 9, Number 4 (December 1957)
pages 299–309

P. H. Saldanha
Department of General Biology
University of Sao Paulo, Brazil

GLASS AND Li (1953) have introduced a statistical model that allows calculations to be made, not only of the intermixture between two base populations but also of the dynamic pattern of the gene flow from one population to another, during a known period of intermixture. The formula derived from Glass and Li is:

To use this formula it is necessary to know: a) the gene frequencies, q₀ and Q, of the base populations; b) the gene frequency, q_k, of the hybrid population; and c) the number of generations, k, of contact between the base populations. The average rates of gene flow (m) from one population to another varies according to the assumed value of k and to the amount of accumulated admixture in the hybrid population. Some limitations of this method have been stressed by Glass and Li.

It should be of interest to compare the process of hybridization between Negro and White populations in Brazil to that in the United States, since the social conditions in the two countries have been and still are different. This is a first attempt to do so.

THE BRAZIL NEGRO

An important problem, which is not yet completely settled, is the African origin of Brazilian Negroes. The comparative ethnography of the Brazilian Negro was worked out, in its fundamental aspects, by the pioneer work of Nina Rodrigues (1932) and the later work of Ramos (1951a). The data on the relations between African and Brazilian cultural groups of Negroes shown in Table I result from these studies…

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Race Crossing in Man (Eugenics Lab. Mem. XXXVI) [Review]

American Journal of Human Genetics
Volume 6, Number 1 (March 1954)
pages 195–196

Kenneth S. Brown
University of Chicago

By J. C. Trevor, New York: Cambridge University Press, 1953, Pp. 45

This brief monograph is a mixed blessing. On one hand it demonstrates what a wealth of metrical material has been collected on human hybrid populations, while on the other it presents methods of analysis which are both inefficient and ineptly applied.

In his preferatory note, Dr. L. S. Penrose points out that this work was done prior to the start of hostilities in 1939, but that the value of the data presented is timeless. This is very true, however the analysis made of the data is rapidly showing signs of age. The data are a compilation of published records of nine outstanding cases of biracial crossing; Hybrid American Negroes, Jamaican ‘Browns’, Half-Blood Sioux, Ojibwa-Whites, Yucatecans, Rehoboth Bastaards, Kisar Mestizos, Norfolk Islanders, and Anglo-Indians. The mean and standard error are recorded for stature and seven cranial measures for most of these populations. Additional measurements are noted for many. In each population studied the sample includes 25 or more adult (20 years or over) individuals of each sex. The values for each sex are recorded separately.

The mean of the hybrid population is compared with that of each of its propositus population groups by the use of Student’s t test. Unfortunately this test requires the assumption that the variances of the populations being compared be the same. Nowhere in the presentation is this recognized. It would have been eminently desirable to determine the significance of the variance ratio for each parameter for each pair of populations compared before the t test was applied. For cases of significant difference in variance between the populations the Fisher-Behrens method for the use of t with samples of unequal variance would be applicable.

The variability of the propositus and hybrid populations is considered separately by the method of Mourant in which the variance ratio of each character for each population pair is found and then the mean variance ratio for each pair determined. This analysis indicated that the variance of the hybrid population is greater, but was found, by a t test, to be significantly greater in only two cases. Here it would have seemed desirable to look up the values in a table of F to get a more powerful estimate of the difference between these populations.

The material presented in this monograph provides a good addition to the blood group, dermatoglyphic, and taster frequency data which are currently used in the analysis of population dynamics, and should serve to attract the attention of interested workers to this relatively undeveloped body of information.

Factors in the Microevolution of a Triracial Isolate

American Journal of Human Genetics
Volume 18, Number 1 (January 1966)
pages 26-38

W. S. Pollitzer
Department of Anatomy
University of North Carolina, Chapel Hill

R. M. Menegaz-Bock
Genetics Training Committe
University of North Carolina, Chapel Hill

J. C. Herion
Department of Medicine
University of North Carolina, Chapel Hill

Triracial Isolates today attract the attention of the anthropologist, the geneticist, and the medical scientist as questions arise concerning the origin of such isolates, their history, social status, breeding structure, and inherited pathological conditions. This paper describes the physical, serological, and clinical characteristics of a hybrid population in northeastern North Carolina (Witkop et al., 1960; Menegaz-Bock, 1962), its racial composition, and the cultural and biological factors in its evolution.

History

The population can be traced at least as far back as the American Revolution. The most common surname in this region today is the same as that of two brothers, said to be descended from Cherokee Indians and whites, who fought in that war. The census of 1790 for the county in which the majority of this population now live lists this name only under the designation “all other free persons;” four of seven other surnames frequent in this population are listed as “free white,” while three are listed under both of these headings. Many of these names, well-known in the isolate today, can be traced through the census reports of the nineteenth century. In 1800, ten are listed, mostly under “free persons of color,” and the census of 1810 lists six of these as “other free persons except Indians not taxed.” By 1820, most of these names appear in the column “free Negro.” Eleven surnames common in the current population are listed in the census of 1830 as “free colored persons,” and most of these are listed under the same heading again in 1840. The census of 1850, designating free inhabitants as “white,” “black,” and “mulatto,” registers a dozen of these family names as “mulattoes” and half of these also as “white.” In 1860, the census for the western district of the county listed 13 of the common names as free inhabitants, either white, black, or mulatto. In the 1870 census for the township where most of the population now lives, five of seven last names common in the group include mulattoes. The census of 1880 contains ten names common in the township now, and all but two of these are to be found under “mulatto.” The census of 1890 was destroyed, and names are not released for the censuses from 1900 on…

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