Abstract
BackgroundWe evaluate the process by which the Americas were originally colonized and propose a three-stage model that integrates current genetic, archaeological, geological, and paleoecological data. Specifically, we analyze mitochondrial and nuclear genetic data by using complementary coalescent models of demographic history and incorporating non-genetic data to enhance the anthropological relevance of the analysis.Methodology/FindingsBayesian skyline plots, which provide dynamic representations of population size changes over time, indicate that Amerinds went through two stages of growth ≈40,000 and ≈15,000 years ago separated by a long period of population stability. Isolation-with-migration coalescent analyses, which utilize data from sister populations to estimate a divergence date and founder population sizes, suggest an Amerind population expansion starting ≈15,000 years ago.Conclusions/SignificanceThese results support a model for the peopling of the New World in which Amerind ancestors diverged from the Asian gene pool prior to 40,000 years ago and experienced a gradual population expansion as they moved into Beringia. After a long period of little change in population size in greater Beringia, Amerinds rapidly expanded into the Americas ≈15,000 years ago either through an interior ice-free corridor or along the coast. This rapid colonization of the New World was achieved by a founder group with an effective population size of ≈1,000–5,400 individuals. Our model presents a detailed scenario for the timing and scale of the initial migration to the Americas, substantially refines the estimate of New World founders, and provides a unified theory for testing with future datasets and analytic methods.
Highlights
Intense and interdisciplinary attention has focused on the colonization of the last habitable landmass on the planetthe peopling of the Americas
This set of 77 complete coding mitochondrial DNA (mtDNA) genomes represents geographically and linguistically diverse populations distributed throughout the New World [3]
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Summary
Intense and interdisciplinary attention has focused on the colonization of the last habitable landmass on the planetthe peopling of the Americas. The first comprehensive, interdisciplinary model for New World colonization incorporated linguistic, paleoanthropological, and genetic data and generated great controversy, which was due at least in part, to the uniquely broad scope of the research [1]. More focused studies have resulted in agreement on the general parameters of the colonization process, such as a single migration in contrast to the original three-migration model that distinguished Amerinds, Na-Dene, and Eskimo-Aleuts [1]. The reduced variation and ubiquitous distribution of mitochondrial and Y chromosome haplogroups and microsatellite diversity throughout the New World relative to Asia argue strongly for a single migration [3,4]. We evaluate the process by which the Americas were originally colonized and propose a three-stage model that integrates current genetic, archaeological, geological, and paleoecological data. We analyze mitochondrial and nuclear genetic data by using complementary coalescent models of demographic history and incorporating nongenetic data to enhance the anthropological relevance of the analysis
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