3 wave to 3 stage models of peopling of the Americas

This is an upcoming article in PlosOne that builds on an article from early last year by Tamm et al. and the idea of a Beringian standstill (blogged about here) and rapid colonization of the Americas using mtDNA data. From my brief cursory reading of the article their argument look pretty plausible and I like how they use a wide array of data to support their hypothesis.

A Three-Stage Colonization Model for the Peopling of the Americas

Andrew Kitchen¹, Michael M. Miyamoto², Connie J. Mulligan^1*

1 Department of Anthropology, University of Florida, Gainesville, Florida, United States of America, 2 Department of Zoology, University of Florida, Gainesville, Florida, United States of America

Abstract

Background

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. 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/Findings

Bayesian 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/Significance

These 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.