The slave trade and the origins of matrilineal kinship.

Matrilineal kinship systems-where descent is traced through mothers only-are present all over the world but are most concentrated in sub-Saharan Africa. We explore the relationship between exposure to Africa's external slave trades, during which millions of people were shipped from the continent during a 400-year period, and the evolution of matrilineal kinship. Scholars have hypothesized that matrilineal kinship, which is well-suited to incorporating new members, maintaining lineage continuity and insulating children from the removal of parents (particularly fathers), was an adaptive response to the slave trades. Motivated by this, we test for a connection between the slave trades and matrilineal kinship by combining historical data on an ethnic group's exposure to the slave trades and the presence of matrilineal kinship following the end of the trades. We find that the slave trades are positively associated with the subsequent presence of matrilineal kinship. The result is robust to a variety of measures of exposure to the slave trades, the inclusion of additional covariates, sensitivity analyses that remove outliers, and an instrumental variables estimator that uses a group's historical distance from the coast as an instrument. We also find evidence of a complementarity between polygyny and matrilineal kinship, which were both social responses to the disruption of the trades. This article is part of the theme issue 'Social norm change: drivers and consequences'.

The ancestry and geographical origins of St Helena's liberated Africans.

The island of St Helena played a crucial role in the suppression of the transatlantic slave trade. Strategically located in the middle of the South Atlantic, it served as a staging post for the Royal Navy and reception point for enslaved Africans who had been "liberated" from slave ships intercepted by the British. In total, St Helena received approximately 27,000 liberated Africans between 1840 and 1867. Written sources suggest that the majority of these individuals came from West Central Africa, but their precise origins are unknown. Here, we report the results of ancient DNA analyses that we conducted as part of a wider effort to commemorate St Helena's liberated Africans and to restore knowledge of their lives and experiences. We generated partial genomes (0.1-0.5×) for 20 individuals whose remains had been recovered during archaeological excavations on the island. We compared their genomes with genotype data for over 3,000 present-day individuals from 90 populations across sub-Saharan Africa and conclude that the individuals most likely originated from different source populations within the general area between northern Angola and Gabon. We also find that the majority (17/20) of the individuals were male, supporting a well-documented sex bias in the latter phase of the transatlantic slave trade. The study expands our understanding of St Helena's liberated African community and illustrates how ancient DNA analyses can be used to investigate the origins and identities of individuals whose lives were bound up in the story of slavery and its abolition.

Historical genomes elucidate European settlement and the African diaspora in Delaware.

The 17th-century colonization of North America brought thousands of Europeans to Indigenous lands in the Delaware region, which comprises the eastern boundary of the Chesapeake Bay in what is now the Mid-Atlantic region of the United States.1 The demographic features of these initial colonial migrations are not uniformly characterized, with Europeans and European-Americans migrating to the Delaware area from other countries and neighboring colonies as single persons or in family units of free persons, indentured servants, or tenant farmers.2 European colonizers also instituted a system of racialized slavery through which they forcibly transported thousands of Africans to the Chesapeake region. Historical information about African-descended individuals in the Delaware region is limited, with a population estimate of less than 500 persons by 1700 CE.3,4 To shed light on the population histories of this period, we analyzed low-coverage genomes of 11 individuals from the Avery's Rest archaeological site (circa 1675-1725 CE), located in Delaware. Previous osteological and mitochondrial DNA (mtDNA) sequence analyses showed a southern group of eight individuals of European maternal descent, buried 15-20 feet from a northern group of three individuals of African maternal descent.5 Autosomal results further illuminate genomic similarities to Northwestern European reference populations or West and West-Central African reference populations, respectively. We also identify three generations of maternal kin of European ancestry and a paternal parent-offspring relationship between an adult and child of African ancestry. These findings expand our understanding of the origins and familial relationships in late 17th and early 18th century North America.

A genetic and linguistic analysis of the admixture histories of the islands of Cabo Verde.

From the 15th to the 19th century, the Trans-Atlantic Slave-Trade (TAST) influenced the genetic and cultural diversity of numerous populations. We explore genomic and linguistic data from the nine islands of Cabo Verde, the earliest European colony of the era in Africa, a major Slave-Trade platform between the 16th and 19th centuries, and a previously uninhabited location ideal for investigating early admixture events between Europeans and Africans. Using local-ancestry inference approaches, we find that genetic admixture in Cabo Verde occurred primarily between Iberian and certain Senegambian populations, although forced and voluntary migrations to the archipelago involved numerous other populations. Inter-individual genetic and linguistic variation recapitulates the geographic distribution of individuals' birth-places across Cabo Verdean islands, following an isolation-by-distance model with reduced genetic and linguistic effective dispersals within the archipelago, and suggesting that Kriolu language variants have developed together with genetic divergences at very reduced geographical scales. Furthermore, based on approximate bayesian computation inferences of highly complex admixture histories, we find that admixture occurred early on each island, long before the 18th-century massive TAST deportations triggered by the expansion of the plantation economy in Africa and the Americas, and after this era mostly during the abolition of the TAST and of slavery in European colonial empires. Our results illustrate how shifting socio-cultural relationships between enslaved and non-enslaved communities during and after the TAST, shaped enslaved-African descendants' genomic diversity and structure on both sides of the Atlantic.

Challenges of accurately estimating sex-biased admixture from X chromosomal and autosomal ancestry proportions.

Sex-biased admixture can be inferred from ancestry-specific proportions of X chromosome and autosomes. In a paper published in the American Journal of Human Genetics, Micheletti et al.1 used this approach to quantify male and female contributions following the transatlantic slave trade. Using a large dataset from 23andMe, they concluded that African and European contributions to gene pools in the Americas were much more sex biased than previously thought. We show that the reported extreme sex-specific contributions can be attributed to unassigned genetic ancestry as well as the limitations of simple models of sex-biased admixture. Unassigned ancestry proportions in the study by Micheletti et al. ranged from ∼1% to 21%, depending on the type of chromosome and geographic region. A sensitivity analysis illustrates how this unassigned ancestry can create false patterns of sex bias and that mathematical models are highly sensitive to slight sampling errors when inferring mean ancestry proportions, making confidence intervals necessary. Thus, unassigned ancestry and the sensitivity of the models effectively prohibit the interpretation of estimated sex biases for many geographic regions in Micheletti et al. Furthermore, Micheletti et al. assumed models of a single admixture event. Using simulations, we find that violations of demographic assumptions, such as subsequent gene flow and/or sex-specific assortative mating, may have confounded the analyses of Micheletti et al., but unassigned ancestry was likely the more important confounding factor. Our findings underscore the importance of using complete ancestry information, sufficiently large sample sizes, and appropriate models when inferring sex-biased patterns of demography. This Matters Arising paper is in response to Micheletti et al.,1 published in American Journal of Human Genetics. See also the response by Micheletti et al.,2 published in this issue.

Community-engaged ancient DNA project reveals diverse origins of 18th-century African descendants in Charleston, South Carolina.

In this study, we present the results of community-engaged ancient DNA research initiated after the remains of 36 African-descended individuals dating to the late 18th century were unearthed in the port city of Charleston, South Carolina. The Gullah Society of Charleston, along with other Charleston community members, initiated a collaborative genomic study of these ancestors of presumed enslaved status, in an effort to visibilize their histories. We generated 18 low-coverage genomes and 31 uniparental haplotypes to assess their genetic origins and interrelatedness. Our results indicate that they have predominantly West and West-Central African genomic ancestry, with one individual exhibiting some genomic affiliation with populations in the Americas. Most were assessed as genetic males, and no autosomal kin were identified among them. Overall, this study expands our understanding of the colonial histories of African descendant populations in the US South.

"The lungs of a ship": Ventilation, acclimatization, and labor in the maritime environment, 1740-1800.

This article examines the connection between projects for shipboard ventilation and the shifting medical discourse about acclimatization in the British Empire during the eighteenth century. I argue that the design, use, and disuse of a class of shipboard "ventilators" proposed by natural philosopher Stephen Hales helps us to trace changing ideas about the ability of European bodies to acclimate, or "season," to tropical environments. These ventilating machines appealed to British administrators because they represented an embodiment of providential and enlightened ideas that validated the expansion of overseas empire. In addition, they promised to increase labor efficiency by reducing the mortality and misery experienced by the sailors and enslaved people during long sea voyages. As skepticism about acclimatization grew in response to stubbornly high mortality rates in the West Indies, Hales' ventilators fell out of favor - a development underscored by their dismissal as a potential solution for the appalling conditions found in the transatlantic slave trade. By examining ventilators' nearly fifty-year career in naval and slave ships, this article will show the role of technology and the shipboard environment in the transition from enlightened optimism about acclimatization toward later attitudes of racial and environmental essentialism.

Association of hepatitis C virus genotype 2 spread with historic slave trade and commerce routes in Western Africa.

The hepatitis C virus genotype 2 (HCV2) is endemic in Western and Central Africa. The HCV2 evolutionary origins remain uncertain due to the paucity of available genomes from African settings. In this study, we investigated the molecular epidemiology of HCV infections in rural Guinea, Western Africa, during 2004 and 2014. Broadly reactive nested reverse transcription polymerase chain reaction (RT-PCR)-based screening of sera from 1,571 asymptomatic adults resulted in the detection of 25 (1.5 per cent; 95 per cent confidence interval 0.9-2.3) positive samples, with a median viral load of 2.54E + 05 IU/ml (interquartile range 6.72E + 05). HCV-infected persons had a median age of 47 years, and 62.5 per cent were male and 37.5 per cent were female. The full polyprotein-encoding genes were retrieved by a combination of high throughput and Sanger sequencing from 17 samples showing sufficiently high viral loads. Phylogenetic analysis and sequence distances ≥13 per cent averaged over the polyprotein genes compared to other HCV2 subtypes revealed nine previously unknown HCV2 subtypes. The time to the most recent common ancestor of the Guinean HCV2 strains inferred in a Bayesian framework was 493 years (95 per cent Highest posterior density (HPD) 453-532). Most of the Guinean strains clustered poorly by location on both the level of sampling sites within Guinea and the level of countries in the phylogenetic reconstructions. Ancestral state reconstruction provided decisive support (Bayes factor > 100) for an origin of HCV2 in Western Africa. Phylogeographic reconstructions in a Bayesian framework pointed to a radial diffusion of HCV2 from Western African regions encompassing today's countries like Ghana, Guinea Bissau, or Burkina Faso, to Central and Northern African regions that took place from the 16th century onwards. The spread of HCV2 coincided in time and space with the main historic slave trade and commerce routes, supported by Bayesian tip-association significance testing (P = 0.01). Our study confirms the evolutionary origins of HCV2 in Western Africa and provides a potential link between historic human movements and HCV2 dispersion.

Conexões entre dois mundos. Prática médica, artes de curar e os saberes locais angolanos nos textos europeus ao longo do século XVIII / Connections between two worlds. Medical practice, healing arts and the local angolan knowledge in european texts throughout the 18th century

As conexões entre a África e o Brasil são tema recorrente na historiografia, principalmente, aquela relacionada com as questões sociais, econômicas, logísticas e políticas que envolviam o tráfico de escravos entre ambos os continentes. Um dos aspectos de maior interesse para os pesquisadores da história das ciências é, nesse sentido, a questão da saúde dos povos escravizados. Neste aspecto, a história da Medicina e dos conhecimentos médicos e farmacêuticos retratam um cenário no qual os contributos dos conhecimentos de origem africana tem vindo a ser verificados. Neste artigo, pretendo reconhecer as práticas médicas aplicadas em território angolano através de uma série de tratados médicos escritos por europeus que praticaram medicina em Angola, mais precisamente em Luanda, pretendendo responder às seguintes questões: Qual é o peso do conhecimento das populações locais na formação dos tratados médicos angolanos? Havia circulação de conhecimentos médicos entre Angola e Brasil?.(AU)

The connections between Africa and Brazil are a recurring theme in historiography, especially that related to social, economic, logistical and political issues involving the slave trade between the two continents. One of the most interesting aspects for researchers in the history of science is, in this sense, the question of the health of enslaved peoples. In this respect, the history of medicine and medical and pharmaceutical knowledge portray a scenario in which the contributions of knowledge of African origin have been verified. In this article, I intend to recognise the medical practices applied in Angolan territory through a series of medical treaties written by Europeans who practised medicine in Angola, more precisely in Luanda, in order to answer the following questions: What is the weight of the local population’s knowledge in the formation of Angolan medical treaties? Was there a circulation of medical knowledge between Angola and Brazil?.(AU)

"Espantosa mortandade": desembarques, demografias e enfermidades africanas / "Appalling mortality": disembarkation, demographics, and African diseases

Resumo Este artigo contribui para conhecermos melhor as condições a que africanos estavam submetidos no imediato desembarque, estendendo o estudo para além do navio. Destaca a importância dos africanos orientais no Sudeste brasileiro no início do século XIX, o que deve ser considerado para o aprofundamento da análise sobre reinvenções identitárias, doenças e práticas de cura. As dores dessas pessoas tiveram como pano de fundo os debates e as negociações políticas em torno da proibição do tráfico atlântico e da independência do Brasil.

Abstract This article contributes to a better understanding of the conditions which Africans endured immediately after landing in Brazil, taking the study beyond what happened in the slave ships. It highlights the importance of Eastern Africans in the southeast of Brazil, in the beginning of the nineteenth century, something that must be considered in order to do a deeper analysis of identity reinventions, diseases, and healing practices. The background of the suffering of those people can be found in the debates and political negotiations surrounding the prohibition of the Atlantic slave trade and the independence of Brazil.

Phylogeography of Sub-Saharan Mitochondrial Lineages Outside Africa Highlights the Roles of the Holocene Climate Changes and the Atlantic Slave Trade.

Despite the importance of ancient DNA for understanding human prehistoric dispersals, poor survival means that data remain sparse for many areas in the tropics, including in Africa. In such instances, analysis of contemporary genomes remains invaluable. One promising approach is founder analysis, which identifies and dates migration events in non-recombining systems. However, it has yet to be fully exploited as its application remains controversial. Here, we test the approach by evaluating the age of sub-Saharan mitogenome lineages sampled outside Africa. The analysis confirms that such lineages in the Americas date to recent centuries-the time of the Atlantic slave trade-thereby validating the approach. By contrast, in North Africa, Southwestern Asia and Europe, roughly half of the dispersal signal dates to the early Holocene, during the "greening" of the Sahara. We elaborate these results by showing that the main source regions for the two main dispersal episodes are distinct. For the recent dispersal, the major source was West Africa, but with two exceptions: South America, where the fraction from Southern Africa was greater, and Southwest Asia, where Eastern Africa was the primary source. These observations show the potential of founder analysis as both a supplement and complement to ancient DNA studies.

Should the USA Offer Reparations to Africa for the Transatlantic Slave Trade?

This article begins with background information on the international social movement for reparations for the transatlantic slave trade. I then propose that the USA ought to offer reparations, including participation in and financing of a truth commission on the slave trade; apology for the harms caused by the trade; and symbolic financial assistance to establish monuments to the slave trade, museums exhibits, and educational programs. The article concludes with a discussion of whether the USA would have the political will to offer reparations to Africa.

Demand for vaccination in Sub-Saharan Africa: The vertical legacy of the slave trade.

We combine historical data on the slave trade by ethnic group with individual-level data geolocated at the cluster level from the 2010-2014 Demographic and Health Surveys to examine the relationship between ancestors' exposure to the slave trade and children vaccination status against measles. Exploiting within-location variation, and hence isolating the vertical cultural transmission channel of the slave trade, we find that children from mothers whose ancestors were exposed to the slave trade are less likely to be vaccinated than children living in the same location but with mothers from a slave-free ethnic group. The effect is larger than that of standard determinants of health demand, such as education or revenue. Exploiting other health behaviors, we point to mistrust as the channel through which the slave trade affects current demand for vaccination. We find evidence of increased adverse effect of slave trade exposure on contemporaneous demand for vaccination among the descendants whose family has a higher preference for traditional practices and higher incentives to transmit their inherited cultural traits. While we know that there is not a uniform health policy code deemed appropriate for all geographical areas, our results suggest that there is space to integrate ethnic groups' historical-specificity in health policy design and communication.

Dinâmica comparada: fluxos dos escravizados africanos em São Paulo, Minas Gerais e Maranhão (1804-1848) / Comparative dynamics: flows of enslaved Africans in São Paulo, Minas Gerais and Maranhão (1804-1848) / Dinámica comparada: flujos de africanos esclavizados en São Paulo, Minas Gerais y Maranhão (1804-1848)

Analisamos comparativamente informes demográficos de qualidade aceitável acerca dos escravizados nascidos na África para Minas Gerais, São Paulo e Maranhão de 1804 a 1848. As parcelas dos nascidos na África em relação aos escravizados e às razões de sexo de todos os cativos, de acordo com as idades, auxiliaram-nos a remontar a dinâmica retrospectiva da chegada dos africanos às regiões. Supondo certas hipóteses e procedimentos, a partir das coortes etárias, estimamos as proporções de africanos e as razões de sexo da população cativa para os períodos anteriores aos das listas nominativas de habitantes. A dinâmica retrospectiva da introdução de africanos reconstruída mostrou-se bastante correlacionada à história econômica das diferentes regiões estudadas.

We compare the surviving enslaved people present in demographic censuses of acceptable quality for Minas Gerais, São Paulo and Maranhão from 1804 to 1848. The share of those born in Africa in relation to slaves and the sex ratio of all captives according to their ages helped us find the retrospective dynamics of the arrival of Africans to these regions. When using age cohorts, we estimate, assuming certain hypotheses and procedures, the proportions of Africans and the sex ratios of the captive population for periods prior to those of the nominative lists of inhabitants. The retrospective dynamics of the reconstructed introduction of these Africans proved to be closely correlated with the economic history of the different regions analyzed.

Analizamos comparativamente a los sobrevivientes esclavizados presentes en los informes demográficos evaluados como de calidad aceptable para Minas Gerais, São Paulo y Maranhão entre 1804 y 1848. La proporción de los nacidos en África en relación con los esclavizados y la proporción de sexos de todos los cautivos, según las edades, nos ayudaron a trazar la dinámica retrospectiva de la llegada de africanos a estas regiones. Utilizando las cohortes de edad, estimamos, asumiendo ciertas hipótesis y procedimientos, las proporciones de africanos y las proporciones de sexos de la población cautiva para períodos anteriores a las listas nominativas de habitantes. La dinámica retrospectiva de la introducción reconstruida de africanos demostró estar altamente correlacionada con la historia económica de las diferentes regiones estudiadas.

The Genes of Freedom: Genome-Wide Insights into Marronage, Admixture and Ethnogenesis in the Gulf of Guinea.

The forced migration of millions of Africans during the Atlantic Slave Trade led to the emergence of new genetic and linguistic identities, thereby providing a unique opportunity to study the mechanisms giving rise to human biological and cultural variation. Here we focus on the archipelago of São Tomé and Príncipe in the Gulf of Guinea, which hosted one of the earliest plantation societies relying exclusively on slave labor. We analyze the genetic variation in 25 individuals from three communities who speak distinct creole languages (Forros, Principenses and Angolares), using genomic data from expanded exomes in combination with a contextual dataset from Europe and Africa, including newly generated data from 28 Bantu speakers from Angola. Our findings show that while all islanders display mixed contributions from the Gulf of Guinea and Angola, the Angolares are characterized by extreme genetic differentiation and inbreeding, consistent with an admixed maroon isolate. In line with a more prominent Bantu contribution to their creole language, we additionally found that a previously reported high-frequency Y-chromosome haplotype in the Angolares has a likely Angolan origin, suggesting that their genetic, linguistic and social characteristics were influenced by a small group of dominant men who achieved disproportionate reproductive success.

From '20. and odd' to 10 million: The growth of the slave population in the United States.

This research note describes the growth of the slave population in the United States and develops several new measures of its size and growth, including an estimate of the total number of slaves who ever lived in the United States. Estimates of the number of births and slave imports are provided in ten-year increments between 1619 and 1860 and in one-year increments between 1861 and 1865. The results highlight the importance of natural increase to the rapid growth of the U.S. slave population and indicate that approximately 10 million slaves lived in the United States, where they contributed 410 billion hours of labor. A concluding discussion highlights a few descriptive statistics historians might find useful, including the cumulative number of slaves who lived in the United States by decade and the proportion of slaves who were living at various moments in U.S. history, including shortly after the ratification of the Constitution in 1788 and at the start of the American Civil War in 1861.

Y Haplogroup Diversity of the Dominican Republic: Reconstructing the Effect of the European Colonization and the Trans-Atlantic Slave Trades.

The Dominican Republic is one of the two countries on the Hispaniola island, which is part of the Antilles. Hispaniola was affected by the European colonization and massive deportation of African slaves since the XVI century and these events heavily shaped the genetic composition of the present-day population. To shed light about the effect of the European rules, we analyzed 92 single nucleotide polymorphisms on the Y chromosome in 182 Dominican individuals from three different locations. The Dominican Y haplogroup composition was characterized by an excess of northern African/European lineages (59%), followed by the African clades (38%), whereas the Native-American lineages were rare (3%). The comparison with the mitochondrial DNA variability, dominated by African clades, revealed a sex-biased admixture pattern, in line with the colonial society dominated by European men. When other Caribbean and non-Caribbean former colonies were also considered, we noted a difference between territories under a Spanish rule (like the Dominican Republic) and British/French rule, with the former characterized by an excess of European Y lineages reflecting the more permissive Iberian legislation about mixed people and slavery. Finally, we analyzed the distribution in Africa of the Dominican lineages with a putative African origin, mainly focusing on central and western Africa, which were the main sources of African slaves. We found that most (83%) of the African lineages observed in Santo Domingo have a central African ancestry, suggesting that most of the slaves were deported from regions.

Genetic Consequences of the Transatlantic Slave Trade in the Americas.

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.

Origin and Health Status of First-Generation Africans from Early Colonial Mexico.

The forced relocation of several thousand Africans during Mexico's historic period has so far been documented mostly through archival sources, which provide only sparse detail on their origins and lived experience. Here, we employ a bioarchaeological approach to explore the life history of three 16th century Africans from a mass burial at the San José de los Naturales Royal Hospital in Mexico City. Our approach draws together ancient genomic data, osteological analysis, strontium isotope data from tooth enamel, δ13C and δ15N isotope data from dentine, and ethnohistorical information to reveal unprecedented detail on their origins and health. Analyses of skeletal features, radiogenic isotopes, and genetic data from uniparental, genome-wide, and human leukocyte antigen (HLA) markers are consistent with a Sub-Saharan African origin for all three individuals. Complete genomes of Treponema pallidum sub. pertenue (causative agent of yaws) and hepatitis B virus (HBV) recovered from these individuals provide insight into their health as related to infectious disease. Phylogenetic analysis of both pathogens reveals their close relationship to strains circulating in current West African populations, lending support to their origins in this region. The further relationship between the treponemal genome retrieved and a treponemal genome previously typed in an individual from Colonial Mexico highlights the role of the transatlantic slave trade in the introduction and dissemination of pathogens into the New World. Putting together all lines of evidence, we were able to create a biological portrait of three individuals whose life stories have long been silenced by disreputable historical events.

Origins, Admixture Dynamics, and Homogenization of the African Gene Pool in the Americas.

The Transatlantic Slave Trade transported more than 9 million Africans to the Americas between the early 16th and the mid-19th centuries. We performed a genome-wide analysis using 6,267 individuals from 25 populations to infer how different African groups contributed to North-, South-American, and Caribbean populations, in the context of geographic and geopolitical factors, and compared genetic data with demographic history records of the Transatlantic Slave Trade. We observed that West-Central Africa and Western Africa-associated ancestry clusters are more prevalent in northern latitudes of the Americas, whereas the South/East Africa-associated ancestry cluster is more prevalent in southern latitudes of the Americas. This pattern results from geographic and geopolitical factors leading to population differentiation. However, there is a substantial decrease in the between-population differentiation of the African gene pool within the Americas, when compared with the regions of origin from Africa, underscoring the importance of historical factors favoring admixture between individuals with different African origins in the New World. This between-population homogenization in the Americas is consistent with the excess of West-Central Africa ancestry (the most prevalent in the Americas) in the United States and Southeast-Brazil, with respect to historical-demography expectations. We also inferred that in most of the Americas, intercontinental admixture intensification occurred between 1750 and 1850, which correlates strongly with the peak of arrivals from Africa. This study contributes with a population genetics perspective to the ongoing social, cultural, and political debate regarding ancestry, admixture, and the mestizaje process in the Americas.