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Post by Admin on Jul 23, 2020 0:40:47 GMT
Last week at the annual conference of the American Society of Human Genetics, 23andMe researchers presented one of the first and largest, broad-scale investigations using genetics to look at the human impact of the transatlantic slave trade.  The research uses genetic connections to Africans found in people living today in the Americas to help bridge the gap in the historical record of the enslavement of Africans. Written records of that history are incomplete. While there are detailed shipping manifests that document the movement of slaves from Africa to various ports in the Americas going back to the early 1500s, there is very little in the way of written records of what happened once they arrived. Beyond that, there is almost no documentation of the illegal slave trade that thrived during much of that time. Bridging Genetic Data and Historical Records The research, presented by Steven Micheletti, Ph.D., a 23andMe population geneticist, offers more details regarding the genetic links between people from different regions of the Americas and people from across Atlantic Africa. The data illustrates how to this day we can see the differences in African ancestry among people of African descent living in different regions of the Americas and how the genetic data closely matches what is known from shipping manifests.  The team used data from more than 50,000 23andMe customers who consented to participate in research and had four grandparents with roots across the Americas and Africa, including participants in 23andMe’s African Genetics Project. The study reveals more clearly how the different eras of the slave trade are reflected in the DNA of populations within the Americas. By using a method for dating the genetic connections between Africa and the Americas, the researchers were able to see that the most recent African ancestry in the Americas traces back to West Central Africa, while the oldest African ancestry traces back to the Windward Coast of Africa and Senegambia. This timing matches the historical record of the slave trade. Anniversary of the First Slaves to North America 23andMe’s research discoveries come on the 400 year anniversary since the first Africans were forcibly brought and enslaved in the United States. The first 20 African slaves were brought to Point Comfort in Virginia in 1619, a year before the pilgrims landed on Plymouth Rock. Ultimately the transatlantic slave trade became the largest forced migration of people in all of human history, taking more than 12.5 million people from Africa towards ports in South America, Central America, the Caribbean, and North America. It is estimated that more than two million died in the holds of slave ships during the harrowing Middle Passage. Of those who survived the Middle Passage, from 3-to-5 percent ended up in North America. The remainder were taken to ports primarily in Central America, the Caribbean or South America. Some of that history can be seen in the genetic data. For instance, the genetic data shows differences among people of African descent within the Americas. Those differences closely align with historical records that show where people from different regions in Africa were brought.  Africans in the Americas For example, people in Brazil and some other regions of South America tend to have higher proportions of Congolese ancestry, while in Central America people have more Senegambian ancestry. Some of these differences across American regions are reflected in the historical record of the slave trade. Some of the genetic trends may be a reflection of ports from which enslaved people were taken, and the shipping routes and destinations that changed over time. During the earliest waves of the slave trade, enslaved Africans were taken primarily from Senegambia and West Central Africa, or what is now known as the Democratic Republic of Congo and Angola. Many of those ships landed in Brazil and the Caribbean. More recent waves of enslaved Africans were taken from ports in the Bights of Benin, West Central Africa, and, possibly, the Windward Coast as well. In addition, the researchers found an African female and European male sex bias. This pattern, which other researchers have reported on previously, reflects the ugly history of sexual exploitation and rape of enslaved women by their slave owners. It also likely reflects the nature of the slave trade itself that among other things included greater isolation of male slaves once they arrived in the Americas. The new study enhances both our understanding of the history of the transatlantic slave trade and its lasting cultural implications for the Americas. PgmNr 2349: The genetic consequences in the Americas of the transatlantic slave trade. Authors: S. Micheletti 1; K. Bryc 1; S. Ancona Esselmann 1; W. Freyman 1; M. Moreno 1; A. Shastri 1; S. Beleza 2; J. Mountain 1 Affiliations: 1) 23andMe, 899 W Evelyn Ave, Mountain View, CA 94041, US; 2) University of Leicester, University Rd, Leicester LE1 7RH, UK The transatlantic slave trade marks the largest forced migration event in history, involving the deportation of an estimated 12.5 million Africans. Occurring between the 15th and 19th centuries, the slave trade involved nearly every country with an Atlantic coastline and has continued to impact the world more than a century after its abolition. Even though shipping records document the number of enslaved people disembarking across the Americas, there have been very few broad-scale genetic studies of populations across all of the Americas with ancestral ties to the transatlantic slave trade. In this study, we utilized high-density genotype data from over 25,000 23andMe research participants with western African ancestry to determine how the transatlantic slave trade has shaped populations across twenty-eight regions within the United States, Latin America, and the Caribbean. Using 23andMe's Ancestry Composition algorithm, which detects ancestry from multiple subregions of western Africa, we show that individuals with African ancestry in the Americas tend to have connections with multiple historical slave trading regions in western Africa. However, the most frequently inferred western African ancestries differ across the Americas. For instance, individuals in the United States and Caribbean tend to have connections with all historical slave trading regions in western Africa, while individuals from Latin America tend to have ancestry primarily from either west central Africa or Senegambia. To estimate the temporal connection between populations in the Americas and West Africa, we identified DNA identical by descent (IBD) between all twenty-eight disembarkment regions and seven historical embarkment regions in western and southwestern Africa. We used the distribution of IBD segment lengths to determine the probability that shared IBD between regions were inherited from a common ancestor who embarked from western Africa during the 400-year period of the transatlantic slave trade. Results suggest that genetic estimates of time to most recent common ancestor are generally concordant with documented embarkment dates from western Africa. Overall, this study provides an unprecedented investigation of the transatlantic slave trade, establishing genetic links between populations in the Americas to populations in western Africa, which has implications for individuals’ understanding of their African roots. |
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Post by Admin on Jul 25, 2020 19:40:13 GMT
 The study found, in line with the major slave route, that most Americans of African descent have roots in territories now located in Angola and the Democratic Republic of Congo. What was surprising was the over-representation of Nigerian ancestry in the US and Latin America when compared with the recorded number of enslaved people from that region. Researchers say this can be explained by the "intercolonial trade that occurred primarily between 1619 and 1807".  They believe enslaved Nigerians were transported from the British Caribbean to other areas, "presumably to maintain the slave economy as transatlantic slave-trading was increasingly prohibited". Likewise, the researchers were surprised to find an underrepresentation from Senegal and The Gambia - one of the first regions from where slaves were deported. Researchers put this down to two grim factors: many were sent to work in rice plantations where malaria and other dangerous conditions were rampant; and in later years larger numbers of children were sent, many of whom did not survive the crossing.  In another gruesome discovery, the study found that the treatment of enslaved women across the Americas had had an impact on the modern gene pool. Researchers said a strong bias towards African female contributions in the gene pool - even though the majority of slaves were male - could be attributed to "the rape of enslaved African women by slave owners and other sexual exploitation". In Latin America, up to 17 African women for every African man contributed to the gene pool. Researchers put this down in part to a policy of "branqueamento", racial whitening, in a number of countries, which actively encouraged the immigration of European men "with the intention to dilute African ancestry through reproduction".  Although the bias in British colonised America was just two African women to one African man, it was no less exploitative. The study highlighted the "practice of coercing enslaved people to having children as a means of maintaining an enslaved workforce nearing the abolition of the transatlantic trade". In the US, women were often promised freedom in return for reproducing and racist policies opposed the mixing of different races, researchers note. Researchers gathered genetic data from 50,000 consenting research participants from both sides of the Atlantic and found that today's genetics reflect the horrors of slavery. Steven Micheletti, a population geneticist at 23andMe, described the study as "one of the most comprehensive investigations of the transatlantic slave trade." "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," he said. |
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Post by Admin on Jul 26, 2020 3:23:04 GMT
Genetic Consequences of the Transatlantic Slave Trade in the Americas
Steven J. Micheletti
Kasia Bryc
Samantha G. Ancona Esselmann
23andMe Research Team
Sandra Beleza
Joanna L. Mountain
Published:July 23, 2020
DOI:https://doi.org/10.1016/j.ajhg.2020.06.012
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.
Introduction
The forced displacement of more than 12.5 million men, women, and children from Africa to the Americas between 1515 and 1865 has had significant social, cultural, health, and genetic impacts across the Americas.1, 2, 3, 4, 5, 6 The consequences of this displacement are myriad and complex, reflecting the varied economic goals and practices of the nations outfitting the ships that transported captive Africans.7,8 The current narrative of this era of forced deportation has been compiled from thousands of historical shipping documents, as well as diaries, personal letters, sketches, and records of slave sales.9 These data suggest that the number of enslaved people disembarking at each port in the Americas, the nation that shipped enslaved people to a given port, and the populations and geographic locations in Africa from which captives were taken differs from region to region within the Americas. For example, shipping manifests indicate that the number of enslaved people disembarking at Brazilian and Caribbean ports was far greater than the number disembarking at other ports in the Americas.5 An estimated 10.1 million enslaved people, primarily male, disembarked in Central America, South America, and the Caribbean (accounting for more than 90% of all captives who were brought to the Americas), with fewer than half a million disembarking in mainland North America5 (3% to 5% of the total).
Concurrent with transatlantic voyages, slave traders also transferred nearly 500,000 enslaved people throughout the Americas with most documented intra-American voyages originating in the Caribbean.5,10 Despite a majority of enslaved Africans disembarking into Latin America, estimates of the proportion of African ancestry for Latin Americans with African roots are lower on average than estimates for African Americans in the United States.11, 12, 13, 14, 15 Further, patterns of embarkation of enslaved populations varied over time, whereby people primarily from 48 distinct ethnolinguistic groups were targeted across Atlantic Africa.16 Prior to 1650, slave voyages most often originated in Senegambia and West Central Africa (in locations now known as the Democratic Republic of Congo and Angola). Although West Central Africa remained a primary embarkation region throughout the slave trading period (from 1650 to 1850), these voyages originated with increasing frequency at ports in the Bight of Benin and the Bight of Biafra, in locations now known as Benin, Nigeria, Cameroon, and Gabon.9
While records have shed light on the main trends of the transatlantic slave trade, the effects of under-documented practices, such as illegal slave trading and details of events after disembarkation in the Americas, remain less understood.17, 18, 19, 20 If under-documented events did not shift the overall paradigm of the slave trade and reproduction rates were equivalent among enslaved populations in the Americas, the degree of genetic similarity between the Americas and each slave-trading region of Africa would be expected to be correlated with the recorded number of enslaved people that disembarked into each region. Also, little is known about the extent to which enslaved people and their descendants continued to associate exclusively with those of similar ethnolinguistic origins after generations in the Americas.21 If such association was common, Americans with African roots would be expected to have African ancestry from a single region of Africa in a pattern that is correlated with geography. Finally, previous studies indicate that individuals with mixed ancestry have higher levels of African ancestry in genomic regions inherited through the female line.22, 23, 24 However, the extent of this sex bias in gene pool contributions may vary across the Americas due to regional differences in mortality of enslaved men,25 rape of enslaved African women,26 forced segregation,21 and practices of reducing African representation by promoting reproduction with Europeans (racial whitening).27,28
Previous genetic studies focusing on people of African descent across the Americas found that most African Americans in the United States have more African ancestry from populations that lived near present-day Nigeria than from populations that lived elsewhere in Atlantic Africa.11,15 However, multiple previous studies have lacked representation of West Central Africa, the largest source of enslaved people during the transatlantic slave trade, leading to an incomplete understanding of the dynamics of population interactions during and after the slave trade era. Here, we combined genetic data from individuals representing the major slave trading regions of Atlantic Africa, Europe, and the Americas and explored concordance with centuries of historical documents. We determined ancestral connections using identity by descent, local ancestry inference, and Bayesian dating techniques. In addition, we used ancestral admixture models to estimate the bias in gene pool contributions of African, European, and indigenous American men and women to current populations of the Americas. We used data from this large, diverse cohort of individuals to obtain unprecedented insights into the genetic impact of the transatlantic slave trade.
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Post by Admin on Jul 26, 2020 23:38:32 GMT
Subjects and Methods Human Subjects We included data from participants drawn from the millions of research participants of 23andMe, Inc., a consumer personal genetics company,29, 30, 31 the 1000 Genomes Project,32 the Human Genome Diversity Project,33 Angola, and previous studies of the Democratic Republic of the Congo,34 Sierra Leone,35 and Khoe-San speaking people.36,37 Angolan participant saliva samples were collected with research consent, which was approved by both the ethics committee of the University 11th of November (Universidade 11 de Novembro), Cabinda, Angola (REf: GD-FM/UoN/2016) and the University of Leicester ethics committee (REf: 11334-sdsb1-genetics). 23andMe research participants provided informed consent and participated in the research online, under a protocol approved by the external AAHRPP-accredited IRB, Ethical & Independent Review Services (E&I Review). 23andMe participants were given the option to fill out web-based questionnaires, including questions on ancestry, ethnicity, and grandparent birth locations. We included in our study data only of customers who signed IRB-approved consent documents, which are explicit about the use of customer data for ancestry research. We grouped individuals across the Americas, Atlantic Africa, and Western Europe into cohorts designed to reflect historical regions (Tables S1–S3). Within the United States, we focused solely on coastal and surrounding states known to have been disembarkation locations for enslaved people.5,9 We included the Cape Verde archipelago as control region since it is an Atlantic African country that was colonized by the Portuguese in the 15th century and has been inhabited primarily by the descendants of enslaved people from Senegambia.38 In Africa, we merged contemporary administrative borders to match all major slave trading regions during the transatlantic slave trade except South East Africa, which constituted about 3.8% of all African embarkments, due to limited sample representation in Mozambique and Madagascar5,9 (Figure 1; Table S1). Because records constitute number of captives deported by region of purchase, as opposed to ethnolinguistic affiliation, merging geographic boundaries in this manner allowed us to connect people of African descent directly to slave trading regions from which their African ancestors may have embarked.5 Borders of Atlantic African countries generally aligned with those historical slave trading regions; however, we split Nigeria into western and eastern states along the Niger River because enslaved people from east of the Niger were deported from ports in the Bight of Biafra, whereas people west of the Niger were deported from ports in the Bight of Benin.9 Categorizing Nigeria in this way also corresponds to the historical geographic occupancy of groups with genetic, ethnic, and linguistic differences: the Yoruba in the Bight of Benin and Esan and Igbo in the Bight of Biafra.4 We considered current Atlantic African populations to be suitable proxies for past populations in Africa given limited migration and current population structure following a latitudinal gradient13,39,40 (Figures S1–S6). We combined regions of Europe participating in the transatlantic slave trade by broad historical descriptors7 and population structure (Figures S7–S9; Table S3), which are largely described by geographic proximity.  Figure 1 Location of Individuals and Cohorts Study participants from the 23andMe customer base indicated their four grandparents were born within the same country (Latin America and the Caribbean) or state (United States), whereas study participants from public databases and Africa-focused studies were included based on self-described historical ties to an African country relevant to the transatlantic slave trade.32, 33, 34, 35 Using 23andMe’s ancestry inference algorithm,41 we excluded data from individuals in the Americas with less than 5% African ancestry, Africans with less than 95% African ancestry, and Europeans with less than 95% European ancestry. We additionally pruned pairs of related individuals using refinedIBD42 so that no two individuals in the study share more than 500 cM of DNA that is identical by descent. These filtering steps reduced a sample size of 183,915 individuals representing the Americas and Africa to 29,339, and 36,866 individuals representing Europe to 20,942. In remaining Atlantic African representatives, we compiled ethnic affiliations from self-reports in 23andMe customers and sample descriptions in other datasets, finding 37 unique ethnic affiliations (Table S1). Genotyping DNA extraction and genotyping of 23andMe customers and Human Genome Diversity Project were performed on saliva samples by the National Genetics Institute (NGI), a CLIA-licensed clinical laboratory and subsidiary of Laboratory Corporation of America. Samples were genotyped on one of five genotyping platforms. The V1 and V2 platforms were variants of the Illumina HumanHap550+ BeadChip, with 560,000 SNPs of which ∼25,000 custom SNPs were selected by 23andMe. The V3 platform was based on the Illumina OmniExpress+ BeadChip, with additional SNPs, totaling about 950,000 SNPs. The V4 and V5 platforms are custom arrays, including a lower-redundancy subset of V2 and V3 SNPs with additional coverage of lower-frequency coding variation and about 570,000 SNPs. Whole-genome genotypes from 1000 Genomes Project32 were subset to match those of V1-V5 platforms and Human Genome Diversity Panel individuals (HGDP)33 were genotyped on both V1 and V5 platforms. Remaining African datasets were genotyped on V3 and V5 platforms. Within each platform, we removed any sample with >5% genotype missingness, producing an average missingness rate of 0.48% across all samples. Population Structure We used both ordination techniques and ADMIXTURE43 to assess population structure within Atlantic Africa as well as in Atlantic Africa plus the Americas. For these techniques, we reduced linkage by pruning SNPs overlapping across all genotype platforms with r2 < 0.5 via PLINK,44 resulting in 43,780 SNPs. We included additional Karitiana, Maya, Pima, and Surui individuals from HGDP23 as Native American references. Ordination techniques consisted of principal component analysis (PCA) and uniform manifold approximation and projection43 (UMAP) using 0.8 minimum distance, 20 nearest neighbors, and number of pcs based on the plateau of eigenvalues (8–15). We ran ADMIXTURE,45 with K values from 2 to 20 in Atlantic African, European, and across all samples. Voyage Records We accessed transatlantic historical records from the Slave Voyages database.5 The Slave Voyages database contains a collection of records from a wide range of published and archival information on more than 36,000 voyages across the Atlantic between 1492 and the early nineteenth century.5 The database contains more than 100 possible variables for each voyage, including voyage dates, disembarkation/embarkation ports, crew information, and voyage outcomes. Some records that lacked pertinent data were imputed using information such as carrying capacity of vessels and characteristics of similar documented voyages.5 Using the Slave Voyages database, we compiled estimates of enslaved African embarkation (“Imputed total num slaves purchased exact”), disembarkation (“Imputed total slaves disembarked exact”), proportions of males (“Imputed percentage male exact”), and proportion of children (“Imputed percentage child exact”) for each Atlantic African (“Imputed principal region of slave purchase lang en exact”) and American region (“Imputed principal port slave dis lang en exact;” “Imputed principal region slave dis lang en exact”), by voyage year (“Imputed arrival at port of dis exact”). For disembarkation estimates of enslaved Africans into the Americas, we mapped the principal port of disembarkation and/or principal region of disembarkation to American region and grouped by Atlantic African region. We estimated shipment sex bias using the “Voyage - percent males on” field and shipment age bias using the “Voyage - percent children on” field. We similarly utilized the intra-American slave trade database, which contains records of voyages within regions of the Americas that occurred in tandem with the transatlantic slave trade.5,46 We aggregated estimates of the number of enslaved people forcefully deported between regions of the Americas using the “Imputed total disembarked,” “Imputed principal place of purchase,” and “Imputed principal place of slave landing” fields.5,46 Identity by Descent We estimated identity by descent (IBD) within and between people representing regions in the Americas, Atlantic Africa, and western Europe using the software package refinedIBD.42 We first removed all missing positions and subset markers to the intersection between all platforms, resulting in 87,847 unique positions used in all IBD analyses. While lowering SNP density may reduce the ability to detect smaller segments, removing missing positions minimizes the detection of false-positive segments.49 With the preference of reducing false-positive calls, we additionally specified a minimum LOD score of 3.3 and a minimum reported length of 3 cM. All other parameters were set to default. We used mean pairwise IBD (msIBD) to assess the overall IBD being shared between (or within) regions whereby msIBD is the sum of IBD shared between populations divided by the total pairwise comparisons of individuals in populations. We used this metric because it accounts for imbalances in sample sizes—although other metrics such as the proportion of individuals with IBD match, skewness of IBD segments, and number of IBD segments shared yield identical patterns (Table S4). We also determined the mean number of regions within Europe or Africa with which individuals from the Americas share a ≥5 cM segment (mcIBD region). That is, an individual from a region in the Americas must share at least 5 cM with a single individual from a region in Europe or Africa to be considered to have an IBD connection to that region. Time to Most Recent Common |
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Post by Admin on Jul 27, 2020 6:46:04 GMT
Results Genetic Connections Compared to Historical Documents The overall correlation between embarkation counts from Africa and mean proportion of identity by descent shared42 (msIBD) between regions of Atlantic Africa and all of the Americas (Figure 2A) is highly significant (Spearman’s coefficient permutation; p < 0.001). However, when we subset shipping records to specific disembarkation regions of the Americas, msIBD and enslaved disembarkation were not significantly correlated across all regions of the Americas (Figures 2B and S10). For example, the study cohorts representing the United States (p = 0.66) and northern South America (p = 0.09) have very little msIBD with Senegambia, compared to the proportion of captives from Senegambia disembarking in those two regions (Figure 2B). Many regions also demonstrate over-representation of msIBD with the Bights of Biafra and Benin compared to historical documents.  Figure 2 IBD Sharing between the Americas and Atlantic Africa versus Documented Counts of Deportation The mean number of IBD connections (mcIBDreg1-reg2; the mean number of regions an individual shares a ≥5 cM IBD segment with) an individual in each region of the Americas has to the seven primary slave trading regions of Africa shows representative individuals from the United States match more slave trading regions (mcIBDUS-Africa = 5.5 ± 2.2) than representative individuals from Central America and Mexico who tend to have IBD connections with fewer regions (mcIBDCentral America - Africa = 2.1 ± 1.7, Figure 2B; Table S5). Of note, there is a particularly strong discordance between disembarkations and mcIBD in Central America and northern South America. There is also a stark difference between mcIBD in the British Caribbean (mcIBD British Caribbean - Africa = 5.8 ± 1.8) versus Latin Caribbean (mcIBD Latin Caribbean - Africa = 3.2 ± 2.1), even though these regions are geographically proximate. These results correspond with comparisons between eight regions of western Europe and regions of the Americas, which indicated that Latin Americans tend to have higher mcIBDLatin America -Europe (x̄ = 4.9 ± 0.76; primarily from Spanish Portuguese) than British occupied regions (x̄ = 3.52 ± 1.1; Figures S11,S12; Table S6). Our Bayesian MCMC approach to estimate time to most recent common ancestor living during the slave trade (TMRCA) from IBD segment lengths predicted that West Central Africa shares more recent common ancestors with individuals in the Americas, whereas Senegambia, Sierra Leone, the Windward Coast, and the Bight of Biafra share earlier common ancestors (Figure 2C). This trend mirrors the majority of embarkation counts out of Africa from temporal historical documents (Figure 2D). Variation in African Ancestry across the Americas Our estimations of African ancestry with 23andMe’s ancestry inference algorithm indicated that mean sub-Saharan African ancestry in Americans with ≥ 5% African ancestry was highest in the British Caribbean (76% ± 20.3%), the United States (71.3% ± 22%), the Guianas (59.7% ± 32.6%), and Cape Verde (45.5% ± 12.6% ; Figure 3). Mean sub-Saharan African ancestry was lowest in Latin America: Latin Caribbean (19.9% ± 12.9%), central South America (13.7% ± 10.5%), northern South America (11.9% ± 8.1%), and Central America plus Mexico (8.9% ± 8.7%). These proportions also correspond with the proportion of African haplogroups in each region (Tables S7 and S8).  Figure 3 Estimated Proportions of African Ancestry across Atlantic Africa, the Americas, and Europe Within 23andMe’s Ancestry Composition hierarchy, there are four local ancestries corresponding to regions in Atlantic Africa: Nigerian (Nigeria), Senegambian (Gambia, Guinea, Guinea-Bissau, Senegal), Coastal West African (Sierra Leone, Ghana, Côte d’Ivoire, Liberia), and Congolese (Angola, Democratic Republic of the Congo). Ancestry inference in the Americas reveals that the majority of individuals within the United States (93%) as well as from the British and French Caribbean (82%) tend to have ancestry from all four of these Atlantic African populations, with Nigerian being the most common of the four. A high proportion of individuals from the Guianas (64%) and the Latin Caribbean (44%) also have ancestry from all four populations, with Coastal West African ancestry in the Guianas being most common relative to other Atlantic African ancestries, and Senegambian being most common in the Latin Caribbean. The plurality (47%) of Mexican and Central American individuals have only Senegambian ancestry, whereas 32% of individuals from northern South America have both Senegambian and Nigerian ancestry. In central South America, the plurality (31%) of individuals have only Congolese ancestry (Figure 3; Table S7). |
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