A new study by anthropologists suggests that first Americans to come to the country 1,000 to 2,000 years earlier than the 13,500 years ago previously thought. The team, led by Ted Goebel, an anthropology professor at Texas A and M, said that their theory indicates that the Americas wasn't settled until as late as 15,000 years ago. He said that their hypothesis, which suggests that the migration from Alaska started about 15,000 years ago, could shift historic timelines.
     To reach their conclusion, the researchers analyzed both archaeological and genetic evidence from several dozen sites throughout the Americas and eastern Asia. The team focused primarily on molecular genetic, archaeological and human skeletal evidence to create a working model that explains the dispersal of modern humans across the New World. They showed that the first Americans came from a single Siberian population and ventured across the Bering land bridge connecting Asia and North America about 22,000 years ago.
     The group got stuck in Alaska because of glacial ice, however, so humans probably didn't migrate down into the rest of the Americas until after 16,500 years ago, when an ice-free corridor in Canada opened up. Previous theories stated that the first migrants spread from Beringia to Tierra del Fuego over a few centuries about. Goebel says scientists have concluded that the peopling of America was a much more complex process. Molecular geneticists have used refined method and an increasing sample of living populations and ancient remains to provide information on the Old World origins of the first Americans, the timing of their initial migration to the New World and the number of major dispersal events. Archaeologists have found new sites and reinvestigated old ones using new methods to explain how early populations colonized North and South America. The team's findings are outlined in a review article in 'Science' magazine titled 'The Late Pleistocene Dispersal of Modern Humans in the Americas.'

Sources: ANI, Science Centric, The Cheers (21 March 2008)