Genetic research sheds light on the population of the Americas

The Americas were settled by three waves of people from Siberia about 15,000 years ago. The way in which the Americas were populated has been a controversial topic in linguistic research; this research seems to prove a theory proposed by linguist Joseph Greenberg many years ago but rejected by many scholars working in the field. Read the short account in the New York Times:

http://www.nytimes.com/2012/07/12/science/earliest-americans-arrived-in-3-waves-not-1-dna-study-finds.html