Reexamining the history of slavery through 23andMe African ancestry data


Date:
July 23, 2020
Source:
Cell Press
Summary:
Researchers have compiled genetic data from consenting 23andMe
research participants to paint a more complete picture of African
ancestry in the New World. By linking genetic data with slave trade
historical records, the findings reinforce harsh truths about
slavery in the Americas and uncover insights into its history,
including the methods used to suppress and exploit Africans once
they disembarked.



FULL STORY ==========================================================================
The effects of the forced deportation of over 10 million African
people during the transatlantic slave trade remain entrenched in the
DNA of people from North, Central, and South America as well as the
Caribbean. Now, in a paper appearing July 23 in the American Journal of
Human Genetics, researchers have compiled genetic data from consenting
23andMe research participants to paint a more complete picture of African ancestry in the New World. By linking genetic data with historical records
of the slave trade, the findings reinforce harsh truths about slavery
in the Americas and uncover new insights into its marked history. These insights include the regions of Africa from which enslaved people were
taken and the methods used to suppress and exploit Africans once they disembarked in the Americas.


==========================================================================
"Our study combined the genetic data of more than 50,000 people on both
sides of the Atlantic with historical records of enslaved people to create
one of the most comprehensive investigations of the transatlantic slave
trade," says first author Steven Micheletti, a population geneticist at 23andMe. "One of the disturbing truths this research revealed was how the mistreatment of people with African ancestry shaped the current genetic landscape of African ancestry in the Americas." The researchers found
that the genetic contributions from major African populations into
the Americas match well with what they expected based on historical
records, with most Americans of African descent having roots in Angola
and Democratic Republic of the Congo. However, a closer look at precise
African regions occasionally revealed a mismatch from what the researchers expected.

For instance, Nigerian ancestry is over-represented in African Americans
in the U.S., likely due to the intra-continental slave trade, which the scientists say has only recently received attention for its impact on
genetic variation. "By examining the Intra-American Slave Trade database,
we concluded that much of the inferred Nigerian ancestry in the United
States derives from transport of slaves within the Americas, primarily
from the Caribbean," says senior author Joanna Mountain, Senior Director
of Research at 23andMe.

In contrast, researchers found that the genetic connections between
African Americans and Senegambians were much lower than expected, given
the number of Senegambians who disembarked in North America. "Because Senegambians were commonly rice cultivators in Africa, they were often transported to rice plantations in the US. These plantations were often
rampant with malaria and had high mortality rates, which may have led
to the reduced genetic representation of Senegambia in African Americans today," Micheletti says.

Both slave-owner and government practices across the Americas had
tremendous impacts on the distribution of African genetics as well. "Many slave-owners in the United States promoted enslaved people having
children with one another for the purpose of maintaining a workforce,
and even after slavery, they tended to segregate people of African
descent," says Micheletti. This is in contrast to practices in parts
of Latin America, which supported "dilution" of the African populace
after slavery was abolished. "In the early 1900s, sources state that
the Brazilian government implemented immigration laws seeking to bring
more Europeans into the country, presumably to have children with darker-skinned females and reduce African ancestry." This practice of "dilution" is one reason the researchers believe that the proportion
of people with greater than 5% African ancestry is five times lower in
Latin America than in the US, despite Latin America receiving roughly 70%
of all disembarked African slaves.

In Latin America, this dilution practice also partially explains why
African women are found to have contributed substantially more to the
gene pool than did African men. "Our analysis estimated about 15 African
women had children for each African man in Central and South America, as
well as the Latin Caribbean," says Micheletti. This female gene bias is
found in North America as well, concordant with reports of generations
of sexual exploitation of African women occurring ubiquitously across
the Americas. Mountain points out that, "The female bias is particularly shocking given that the majority of enslaved individuals were male."
The researchers hope that, with this study, they can help those of
African descent not only to find their roots, but also to understand
how the experiences of their ancestors have shaped the genetic makeup of
their communities. "This paper conveys how the racist and dehumanizing
acts endemic to the slave trade led to different patterns of African
ancestry across the Americas that we can see in the DNA of people living
today. We hope readers grasp not only the impact of the slave trade
but also the deep contributions enslaved Africans made to the history,
economy, and culture of the Americas," says Micheletti.


========================================================================== Story Source: Materials provided by Cell_Press. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Steven J. Micheletti, Kasia Bryc, Samantha G. Ancona Esselmann,
William
A. Freyman, Meghan E. Moreno, G. David Poznik, Anjali J. Shastri,
Sandra Beleza, Joanna L. Mountain, M. Agee, S. Aslibekyan, A. Auton,
R. Bell, S.

Clark, S. Das, S. Elson, K. Fletez-Brant, P. Fontanillas,
P. Gandhi, K.

Heilbron, B. Hicks, D. Hinds, K. Huber, E. Jewett, Y. Jiang,
A. Kleinman, K. Lin, N. Litterman, J. McCreight, M. McIntyre,
K. McManus, S.

Mozaffari, P. Nandakumar, L. Noblin, C. Northover, J. O'Connell, A.

Petrakovitz, S. Pitts, J. Shelton, S. Shringarpure, C. Tian,
J. Tung, R.

Tunney, V. Vacic, X. Wang, A. Zare. Genetic Consequences of the
Transatlantic Slave Trade in the Americas. The American Journal
of Human Genetics, 2020; DOI: 10.1016/j.ajhg.2020.06.012 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200723115919.htm

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