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.

Ancient mitogenomes from the Southern Pampas of Argentina reflect local differentiation and limited extra-regional linkages after rapid initial colonization.

OBJECTIVE: This study aims to contribute to the recovery of Indigenous evolutionary history in the Southern Pampas region of Argentina through an analysis of ancient complete mitochondrial genomes. MATERIALS AND METHODS: We generated DNA data for nine complete mitogenomes from the Southern Pampas, dated to between 2531 and 723 cal BP. In combination with previously published ancient mitogenomes from the region and from throughout South America, we documented instances of extra-regional lineage-sharing, and estimated coalescent ages for local lineages using a Bayesian method with tip calibrations in a phylogenetic analysis. RESULTS: We identified a novel mitochondrial haplogroup, B2b16, and two recently defined haplogroups, A2ay and B2ak1, as well as three local haplotypes within founder haplogroups C1b and C1d. We detected lineage-sharing with ancient and contemporary individuals from Central Argentina, but not with ancient or contemporary samples from North Patagonian or Littoral regions of Argentina, despite archeological evidence of cultural interactions with the latter regions. The estimated coalescent age of these shared lineages is ~10,000 years BP. DISCUSSION: The history of the human populations in the Southern Pampas is temporally deep, exhibiting long-term continuity of mitogenome lineages. Additionally, the identification of highly localized mtDNA clades accords with a model of relatively rapid initial colonization of South America by Indigenous communities, followed by more local patterns of limited gene flow and genetic drift in various South American regions, including the Pampas.

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.

Beyond Serial Founder Effects: The Impact of Admixture and Localized Gene Flow on Patterns of Regional Genetic Diversity.

Geneticists have argued that the linear decay in within-population genetic diversity with increasing geographic distance from East Africa is best explained by a phylogenetic process of repeated founder effects, growth, and isolation. However, this serial founder effect (SFE) process has not yet been adequately vetted against other evolutionary processes that may also affect geospatial patterns of diversity. Additionally, studies of the SFE process have been largely based on a limited 52-population sample. In this modestly updated article, originally published in Human Biology in 2016 (vol. 88, no. 3, pp. 219-231), we assess the effects of founder effect, admixture, and localized gene flow processes on patterns of global and regional diversity using a published data set of 645 autosomal microsatellite genotypes from 5,415 individuals in 248 widespread populations. We used a formal tree-fitting approach to explore the role of founder effects. The approach involved fitting global and regional population trees to extant patterns of gene diversity and then systematically examining the deviations in fit. We also informally tested the SFE process using linear models of gene diversity versus waypoint geographic distances from Africa. We tested the role of localized gene flow using partial Mantel correlograms of gene diversity versus geographic distance controlling for the confounding effects of treelike genetic structure. We corroborate previous findings that global patterns of diversity, both within and between populations, are the product of an out-of-Africa SFE process. Within regions, however, diversity within populations is uncorrelated with geographic distance from Africa. Here, patterns of diversity have been largely shaped by recent interregional admixture and secondary range expansions. Our detailed analyses of the pattern of diversity within and between populations reveal that the signatures of different evolutionary processes dominate at different geographic scales. These findings have important implications for recent publications on the biology of race. Our new foreword situates these findings in a long line of anthropological research that categorically rejects racial interpretations of analyses of human diversity.

Ancestry, health, and lived experiences of enslaved Africans in 18th century Charleston: An osteobiographical analysis.

OBJECTIVES: In 2013, the burials of 36 individuals of putative African ancestry were discovered during renovation of the Gaillard Center in downtown Charleston, South Carolina. The Charleston community facilitated a bioarchaeological and mitogenomic study to gain insights into the lives of these unknown persons, referred to as the Anson Street Ancestors, including their ancestry, health, and lived experiences in the 18th century. METHODS: Metric and morphological assessments of skeletal and dental characteristics were recorded, and enamel and cortical bone strontium stable isotope values generated. Whole mitochondrial genomes were sequenced and analyzed. RESULTS: Osteological analysis identified adults, both females and males, and subadults at the site, and estimated African ancestry for most individuals. Skeletal trauma and pathology were infrequent, but many individuals exhibited dental decay and abscesses. Strontium isotope data suggested these individuals mostly originated in Charleston or sub-Saharan Africa, with many being long-term residents of Charleston. Nearly all had mitochondrial lineages belonging to African haplogroups (L0-L3, H1cb1a), with two individuals sharing the same L3e2a haplotype, while one had a Native American A2 mtDNA. DISCUSSION: This study generated detailed osteobiographies of the Anson Street Ancestors, who were likely of enslaved status. Our results indicate that the Ancestors have diverse maternal African ancestries and are largely unrelated, with most being born locally. These details reveal the demographic impact of the trans-Atlantic slave trade. Our analysis further illuminates the lived experiences of individuals buried at Anson Street, and expands our understanding of 18th century African history in Charleston.

Ancient genomes in South Patagonia reveal population movements associated with technological shifts and geography.

Archaeological research documents major technological shifts among people who have lived in the southern tip of South America (South Patagonia) during the last thirteen millennia, including the development of marine-based economies and changes in tools and raw materials. It has been proposed that movements of people spreading culture and technology propelled some of these shifts, but these hypotheses have not been tested with ancient DNA. Here we report genome-wide data from 20 ancient individuals, and co-analyze it with previously reported data. We reveal that immigration does not explain the appearance of marine adaptations in South Patagonia. We describe partial genetic continuity since ~6600 BP and two later gene flows correlated with technological changes: one between 4700-2000 BP that affected primarily marine-based groups, and a later one impacting all <2000 BP groups. From ~2200-1200 BP, mixture among neighbors resulted in a cline correlated to geographic ordering along the coast.

Ancient DNA and bioarchaeological perspectives on European and African diversity and relationships on the colonial Delaware frontier.

OBJECTIVES: Ancient DNA (aDNA) and standard osteological analyses applied to 11 skeletons at a late 17th to early 18th century farmstead site in Delaware to investigate the biological and social factors of settlement and slavery in colonial America. MATERIALS AND METHODS: Osteological analysis and mitochondrial DNA (mtDNA) sequencing were conducted for all individuals and the resulting data contextualized with archaeological and documentary evidence. RESULTS: Individuals of European and African descent were spatially separated in this colonial cemetery. The skeletal remains exhibited differences in osteological features and maternal genetic ancestry. A specific mtDNA haplotype appeared in a subset of the European-descended individuals suggesting they were maternally related. Individuals of African descent were not maternally related, and instead showed a diversity of haplotypes affiliated with present-day Western, Central, and Eastern regions of Africa. DISCUSSION: Along with the bioarchaeological and documentary evidence, the aDNA findings contribute to our understanding of life on the colonial Delaware frontier. Evidence of maternal relatedness among European-descended individuals at the site demonstrates kin-based settlements in 17th century Delaware and provides preliminary identifications of individuals. The maternal genetic diversity of the individuals with African descent aligns with the routes of the trans-Atlantic slave trade but broadens our understanding of the ancestries of persons involved in it. Burial positioning, osteological pathology, and lack of maternal kinship among individuals of African descent provide tangible evidence for the emergence of racialized labor and society in Delaware during the late 17th century.

The persistence of human DNA in soil following surface decomposition.

Though recent decades have seen a marked increase in research concerning the impact of human decomposition on the grave soil environment, the fate of human DNA in grave soil has been relatively understudied. With the purpose of supplementing the growing body of literature in forensic soil taphonomy, this study assessed the relative persistence of human DNA in soil over the course of decomposition. Endpoint PCR was used to assess the presence or absence of human nuclear and mitochondrial DNA, while qPCR was used to evaluate the quantity of human DNA recovered from the soil beneath four cadavers at the University of Tennessee's Anthropology Research Facility (ARF). Human nuclear DNA from the soil was largely unrecoverable, while human mitochondrial DNA was detectable in the soil throughout all decomposition stages. Mitochondrial DNA copy abundances were not significantly different between decomposition stages and were not significantly correlated to soil edaphic parameters tested. There was, however, a significant positive correlation between mitochondrial DNA copy abundances and the human associated bacteria, Bacteroides, as estimated by 16S rRNA gene abundances. These results show that human mitochondrial DNA can persist in grave soil and be consistently detected throughout decomposition.

Social Identity in New Mexicans of Spanish-Speaking Descent Highlights Limitations of Using Standardized Ethnic Terminology in Research.

In this study, we evaluated the extent to which regional history has shaped the social identity nomenclature in New Mexicans of Spanish-speaking descent (NMSD). We asked 507 NMSD to list the social-identity terms they used to describe themselves and their parents, and we examined the correspondence between these choices and family ties to the region, birthplace, and continental ancestry. NMSD frequently identified using the regional terms "Nuevomexicano/a" (15%) and "Spanish" (12%). These individuals reported family ties to the region that predate New Mexican statehood. They and their parents were frequently born in New Mexico, frequently chose the other of the two terms as a secondary descriptor, and frequently ascribed one of the two terms to their parents. About 10% of NMSD identified as "Mexican American" and "Mexican." About 25% of these individuals, and more than half of their parents, were born in Mexico. They also frequently chose the other of the two terms as a secondary descriptor and frequently ascribed one of the two terms to their parents. Compared to NMSD who identified as "Mexican" and "Mexican American," individuals who identified as "Nuevomexicano/a" and "Spanish" had higher European ancestry and lower Native American and African ancestry. Our results also suggest that the term "Hispanic," frequently chosen as both a primary and secondary social identity term by NMSD, may, as it continues to rise in prominence, mask more deeply rooted and potential socially relevant aspects of social identity in New Mexico. More broadly, these results indicate that regional history influences social identity nomenclatures in ways that are potentially incompatible with US Office of Management and Budget standards. This incompatibility may adversely affect the ability of researchers in the social sciences to assess the causes of social inequality and health disparities in individuals of Spanish-speaking descent in different regions of the United States. We argue that future studies would benefit from more fine-grained, region-specific analyses of social identity.

Beyond Serial Founder Effects: The Impact of Admixture and Localized Gene Flow on Patterns of Regional Genetic Diversity.

Geneticists have argued that the linear decay in within-population genetic diversity with increasing geographic distance from East Africa is best explained by a phylogenetic process of repeated founder effects, growth, and isolation. However, this serial founder effect (SFE) process has not yet been adequately vetted against other evolutionary processes that may also affect geospatial patterns of diversity. Additionally, studies of the SFE process have been largely based on a limited 52-population sample. Here, we assess the effects of founder effect, admixture, and localized gene flow processes on patterns of global and regional diversity using a published data set of 645 autosomal microsatellite genotypes from 5,415 individuals in 248 widespread populations. We used a formal tree-fitting approach to explore the role of founder effects. The approach involved fitting global and regional population trees to extant patterns of gene diversity and then systematically examining the deviations in fit. We also informally tested the SFE process using linear models of gene diversity versus waypoint geographic distances from Africa. We tested the role of localized gene flow using partial Mantel correlograms of gene diversity versus geographic distance controlling for the confounding effects of treelike genetic structure. We corroborate previous findings that global patterns of diversity, both within and between populations, are the product of an out-of-Africa SFE process. Within regions, however, diversity within populations is uncorrelated with geographic distance from Africa. Here, patterns of diversity have been largely shaped by recent interregional admixture and secondary range expansions. Our detailed analyses of the pattern of diversity within and between populations reveal that the signatures of different evolutionary processes dominate at different geographic scales. These findings have important implications for recent publications on the biology of race.

The apportionment of human diversity revisited.

OBJECTIVES: Studies of the apportionment of human genetic diversity have found that local populations harbor nearly as much diversity as the species as a whole. These studies have been a valuable cornerstone in rejecting race as a biological framework in anthropology. The current study presents new analyses that use updated statistical methods based on bifurcating trees to assess the structure of human genetic diversity and its implications for the existence of canonical biological races. MATERIALS AND METHODS: We examine patterns of both goodness-of-fit and lack-of-fit of two bifurcating trees to patterns of diversity determined from autosomal short tandem repeat genotypes in 1,037 people representing 52 populations with worldwide distribution. RESULTS: From goodness-of-fit, we infer a root for the tree within Africa, and we recapitulate a pattern of decreasing genetic diversity with increasing geographic distance from Africa. From lack-of-fit, we present tentative evidence for admixture events with archaic hominins. We do not find evidence that long-range migration or local gene flow have contributed appreciably to the lack of fit at a global scale. CONCLUSION: This is the first study to find a root for a tree of human populations without comparison to a nonhuman out-group, and it is one of the first studies to identify a signature of admixture with archaic hominins without reference to ancient DNA. Our findings complement previous studies of the apportionment of human diversity and provide a more solid evolutionary foundation for the rejection of biological race. Am J Phys Anthropol 160:561-569, 2016. © 2015 Wiley Periodicals, Inc.

Population genetic structure of traditional populations in the Peruvian Central Andes and implications for South American population history.

Molecular-based characterizations of Andean peoples are traditionally conducted in the service of elucidating continent-level evolutionary processes in South America. Consequently, genetic variation among "western" Andean populations is often represented in relation to variation among "eastern" Amazon and Orinoco River Basin populations. This west-east contrast in patterns of population genetic variation is typically attributed to large-scale phenomena, such as dual founder colonization events or differing long-term microevolutionary histories. However, alternative explanations that consider the nature and causes of population genetic diversity within the Andean region remain underexplored. Here we examine population genetic diversity in the Peruvian Central Andes using data from the mtDNA first hypervariable region and Y-chromosome short tandem repeats among 17 newly sampled populations and 15 published samples. Using this geographically comprehensive data set, we first reassessed the currently accepted pattern of western versus eastern population genetic structure, which our results ultimately reject: mtDNA population diversities were lower, rather than higher, within Andean versus eastern populations, and only highland Y-chromosomes exhibited significantly higher within-population diversities compared with eastern groups. Multiple populations, including several highland samples, exhibited low genetic diversities for both genetic systems. Second, we explored whether the implementation of Inca state and Spanish colonial policies starting at about ad 1400 could have substantially restructured population genetic variation and consequently constitute a primary explanation for the extant pattern of population diversity in the Peruvian Central Andes. Our results suggest that Peruvian Central Andean population structure cannot be parsimoniously explained as the sole outcome of combined Inca and Spanish policies on the region's population demography: highland populations differed from coastal and lowland populations in mtDNA genetic structure only; highland groups also showed strong evidence of female-biased gene flow and/or effective sizes relative to other Peruvian ecozones. Taken together, these findings indicate that population genetic structure in the Peruvian Central Andes is considerably more complex than previously reported and that characterizations of and explanations for genetic variation may be best pursued within more localized regions and defined time periods.

Inferring population continuity versus replacement with aDNA: a cautionary tale from the Aleutian Islands.

In The Aleutian and Commander Islands and Their Inhabitants (Philadelphia: Wistar Institute of Anatomy and Biology, 1945), Hrdlicka proposed a population replacement event in the Aleutian Islands approximately 1,000 years ago based on a perceived temporal shift in cranial morphology. However, the archaeological record indicates cultural, and presumed population, continuity for more than 4,000 years. We use mtDNA haplogroup data in the series of prehistoric eastern Aleutian samples (n = 86) studied craniometrically by Hrdlicka to test alternative hypotheses regarding population continuity or replacement in the region. This molecular characterization, in conjunction with direct dating of individual specimens, provided increased resolution for hypothesis testing. Results indicate an apparent shift in mtDNA haplogroup frequencies in the eastern Aleutians approximately 1,000 years ago, in concert with changes in mortuary practices and isotopic signatures reflecting resource acquisition strategies. The earliest Aleut populations were characterized by a high frequency of haplogroup A, as are most modern populations of the North American arctic. Later prehistoric peoples in the Aleutians were characterized by a high frequency of haplogroup D and a correspondingly lower frequency of haplogroup A, a pattern typified by modern Aleut populations.

Population continuity or replacement? A novel computer simulation approach and its application to the Numic expansion (Western Great Basin, USA).

In a previous study, Kaestle and Smith [Am J Phys Anthropol 115 (2001) 1-12] supported a recent (A.D. 1000) Numic expansion into the Great Basin region based on a molecular and statistical analysis of mitochondrial DNA (mtDNA) of ancient and modern native inhabitants of the region. Their statistical methodology could not rule out the possibility that observed differences in haplogroup frequencies are instead the result of long-term microevolutionary change within a single population. To distinguish more effectively between a Numic expansion versus population continuity, we employed a novel computer simulation approach that incorporates microevolutionary factors likely to affect human population genetic variation. We test whether the observed differences in haplogroup frequencies between ancient and modern Great Basin groups could have been produced solely via in situ microevolutionary change. Our results indicate that for reasonable demographic conditions, the observed genetic differences between the observed samples are consistent with population continuity if gene flow among prehistoric Great Basin local groups was less than 1% of local group size per generation. Our analysis also supports a recent population expansion if gene flow between neighboring groups exceeded 8% of local group size per generation. The simulations demonstrate that relatively low gene flow levels and random genetic drift can produce the observed degree of genetic differences between population samples. Although this study focuses on the Numic expansion, this simulation approach can be applied to any geographic region for which genetic data have been collected to address similar questions of population relationships over time.

Is the genetic structure of Gran Chaco populations unique? Interregional perspectives on native South American mitochondrial DNA variation.

This study reevaluates the hypothesis in Demarchi et al. (2001 Am. J. Phys. Anthropol. 115:199-203) that Gran Chaco peoples demonstrate a unique pattern of genetic diversity due to a distinct regional population history. Specifically, they found populations in the central part of the Gran Chaco, or Central Chaco, to have higher within- and lower between-population mitochondrial DNA (mtDNA) haplogroup frequency variation compared to populations in other South American regions. To test this hypothesis of regional uniqueness, we applied analytical and simulation methods to mtDNA first hypervariable (HVI) region sequence data from a broad set of comparative South and Central American population samples. Contrary to the results of Demarchi et al. (2001 Am. J. Phys. Anthropol. 115:199-203), we found that the Gran Chaco's regional within-population diversity is about average among regions, and populations are highly differentiated from each other. When we limited the scale of analysis to the Central Chaco, a more localized subregion of the Gran Chaco, our results fell more in line with the original findings of Demarchi et al. (2001 Am. J. Phys. Anthropol. 115:199-203). Still, we conclude that neither the Gran Chaco regional pattern, nor the Central Chaco subregional pattern, is unique within South America. Nonetheless, the Central Chaco pattern accords well with the area's history, including pre-European contact lifeways and the documented historical use of the area as an interregional crossroads. However, we cannot exclude post-European contact disruption of traditional mating networks as an equally plausible explanation for the observed diversity pattern. Finally, these results additionally inform broader models of South American genetic diversity. While other researchers proposed an east-west continental division in patterns of genetic variation (e.g., Fuselli et al. 2003 Mol. Biol. Evol. 20:1682-1691), we found that in the geographically intermediate Central Chaco, a strict east-west divide in genetic variation breaks down. We suggest that future genetic characterizations of the continent, and subsequent interpretations of evolutionary history, involve a broad regional sampling of South American populations.