COPENHAGEN, DENMARK—A new large-scale genome study is adding to the debate over how the peopling of the Americas occurred. An international team of scientists sampled several present-day Native American and Siberian populations, in addition to ancient DNA samples from across the Americas. “Our study presents the most comprehensive picture of the genetic prehistory of the Americas to date. We show that all Native Americans, including the major sub-groups of Amerindians and Athabascans, descend from the same migration wave into the Americas. This was distinct from later waves that gave rise to the Paleo-Eskimo and Inuit populations in the New World Arctic region,” Maanasa Raghavan of the Centre for GeoGenetics at the University of Copenhagen said in a press release. The results also indicate that the initial migration took place no earlier than 23,000 years ago, when Native Americans split from East Asian and Siberian populations. Ancestral Native Americans may then have been isolated in Beringia for some 8,000 years, since the oldest archaeological evidence in the Americas is about 15,000 years old. The study also found that some 13,000 years ago, this population split into northern and southern branches. Gene flow between some Native American groups and present-day East Asians and Australo-Melanesians was also detected. “It is a surprising finding and it implies that New World populations were not completely isolated from the Old World after their initial migration. We cannot say exactly how and when this gene flow happened, but one possibility is that it came through the Aleutian Islanders living off the coast of Alaska,” added Eske Willerslev, who headed the study. To read more about the peopling of the New World, go to "America, in the Beginning."