University of Michigan population geneticist Noah Rosenberg has collaborated with others to publish a paper in PLoS Genetics that looks at the genetic ancestry of Native Americans. It's part of a journal club that's hosted at the Computational Biology and Evolution blog. In the paper, they examine microsatellite markers of 29 Native American populations from Canada, Central America, and South America, and find evidence, according to Rosenberg, of one single migration from Siberia.