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.