MBE Advance Access published online on October 5, 2009
Molecular Biology and Evolution, doi:10.1093/molbev/msp238
Research Article |
A statistical evaluation of models for the initial settlement of the American continent emphasizes the importance of gene flow with Asia
a Computational and Molecular Population Genetics (CMPG), Institute of Ecology and Evolution, University of Bern, CH-3012 Bern, Switzerland
b Swiss Institute of Bioinformatics, 1025 Lausanne
c Department of Genetics, Federal University of Rio Grande do Sul, 91501-970 Porto Alegre, RS, Brazil
d The Galton Laboratory, Department of Genetics, Evolution and Environment, University College London, London NW1 2HE, United Kingdom
* To whom correspondence may be addressed: Computational and Molecular Population Genetics (CMPG), Institute of Ecology and Evolution, University of Bern, CH-3012 Bern, Switzerland. Phone: +41 31 631 30 31, Fax: +41 31 631 48 88. E-mail: laurent.excoffier{at}iee.unibe.ch
Received for publication June 8, 2009. Revision received September 28, 2009. Accepted for publication October 1, 2009.
While there is agreement in that the Bering Strait was the entry point for the initial colonization of the American continent, there is considerable uncertainty regarding the timing and pattern of human migration from Asia to America. In order to perform a statistical assessment of the relative probability of alternative migration scenarios and to estimate key demographic parameters associated with them, we used an Approximate Bayesian Computation (ABC) framework to analyze a dataset of 401 autosomal microsatellite loci typed in 29 Native American populations. A major finding is that a single, discrete, wave of colonization is highly inconsistent with observed levels of genetic diversity. A scenario with two discrete migration waves is also not supported by the data. The current genetic diversity of Amerindian populations is best explained by a third model involving recurrent gene flow between Asia and America, after initial colonization. We estimate that this colonization involved about 100 individuals and occurred some 13,000 years ago; in agreement with well established archeological data.
Key Words: Human settlement • colonization • Amerindians • Approximate Bayesian Computation • model choice