C&B Notes

Three Waves of American Migration

A genome research study of Native Americans has found that the Western Hemisphere was populated by at least three distinct migrations from Asia.

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.

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[The research team] cannot date the migration from their genomic data but accept the estimate by others that the migration occurred around 15,000 years ago.  This was in the window of time that occurred after the melting of great glaciers that blocked passage from Siberia to Alaska, and before the rising waters at the end of the last ice age submerged Beringia, the land bridge between them.

They also find evidence for two further waves of migration, one among Na-Dene speakers and the other among Eskimo-Aleut, again as Dr. Greenberg predicted.  But whereas Dr. Greenberg’s proposal suggested that three discrete groups of people were packed into the Americas, the new genome study finds that the second and third waves mixed in with the first.  Eskimos inherit about half of their DNA from the people of the first migration and half from a second migration.  The Chipewyans of Canada, who speak a Na-Dene language, have 90 percent of their genes from the first migration and some 10 percent from a third.

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