Abstract
European and African descendants settled the continental US during the 17th-19th centuries, coming into contact with established Native American populations. The resulting admixture among these groups yielded a significant reservoir of Native American ancestry in the modern US population. We analyzed the patterns of Native American admixture seen for the three largest genetic ancestry groups in the US population: African descendants, Western European descendants, and Spanish descendants. The three groups show distinct Native American ancestry profiles, which are indicative of their historical patterns of migration and settlement across the country. Native American ancestry in the modern African descendant population does not coincide with local geography, instead forming a single group with origins in the southeastern US, consistent with the Great Migration of the early 20th century. Western European descendants show Native American ancestry that tracks their geographic origins across the US, indicative of ongoing contact during westward expansion, and Native American ancestry can resolve Spanish descendant individuals into distinct local groups formed by more recent migration from Mexico and Puerto Rico. We found an anomalous pattern of Native American ancestry from the US southwest, which most likely corresponds to the Nuevomexicano descendants of early Spanish settlers to the region. We addressed a number of controversies surrounding this population, including the extent of Sephardic Jewish ancestry. Nuevomexicanos are less admixed than nearby Mexican-American individuals, with more European and less Native American and African ancestry, and while they do show demonstrable Sephardic Jewish ancestry, the fraction is no greater than seen for other New World Spanish descendant populations.
Highlights
Native Americans inhabited the area that makes up the continental US for thousands of years prior to the arrival of the first European settlers
We ask how the historical processes of migration and settlement affected the distribution of Native American admixture across the continental US (S1 Fig). We address this question for the three largest genetic ancestry groups in the modern US population: African descendants (AD), Western European descendants (WD), and Spanish descendants (SD)
The first aim of our study was to characterize the major genetic ancestry groups for the continental US based on observable patterns of ancestry and admixture seen for the 15,620 individuals from the Health and Retirement Study (HRS) analyzed here
Summary
Native Americans inhabited the area that makes up the continental US for thousands of years prior to the arrival of the first European settlers. The ancestors of modern Native Americans are thought have arrived in the Americas from Asia, by way of the Bering Strait, in several successive waves of migration [1]. The current model, based on archaeology and comparative genomic studies, holds that the earliest ancestors of Native Americans arrived in the Americas ~23,000 years ago [2]. The earliest evidence for Native Americans in the continental US dates to ~14,000 years ago [3]. Native American population numbers declined rapidly in the face of continuous immigration, settlement, and conflict, and as a result the modern US population is made up mainly of descendants of European and African immigrants
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