North and South America were first populated by three waves of migrants from Siberia rather than just a single migration, say researchers who have studied the whole genomes of Native Americans in South America and Canada.

Some scientists assert that the Americas were peopled in one large migration from Siberia that happened about 15,000 years ago, but the new genetic research shows that this central episode was followed by at least two smaller migrations from Siberia, one by people who became the ancestors of today’s Eskimos and Aleutians and another by people speaking Na-Dene, whose descendants are confined to North America. The research was published online Wednesday in the journal Nature.

The finding vindicates a proposal first made on linguistic grounds by Joseph Greenberg, the great classifier of the world’s languages. He asserted in 1987 that most languages spoken in North and South America were derived from the single mother tongue of the first settlers from Siberia, which he called Amerind. Two later waves, he surmised, brought speakers of Eskimo-Aleut and of Na-Dene, the language family spoken by the Apache and Navajo....