Population genetics. Genes suggest three groups peopled the New World.

Who were the first Americans? Twenty years ago, in a bold synthesis of linguistic, genetic, and dental data, researchers proposed that the first people on this continent arrived from Asia in at least three distinct waves. But the idea of diverse origins slowly fell out of favor, in part because studies found that Native Americans from Alaska to Chile were genetically similar, suggesting a single founding population. Now the most comprehensive genetic study to date concludes that Native Americans do indeed descend from at least three groups of ancestors from Asia. But in contrast to the original three-wave hypothesis, the researchers found that once in the New World, all three source populations intermingled extensively.