Ancient America, 40,000-1500 B.C.

Land Bridge.

The first immigrants to North America came to the continent between 40,000 and 10,000 B.C. in two large movements timed to the rhythmic shrinking and expanding of the world's seas. Between what is today Alaska and Siberia a land bridge sixty miles long and athousand miles wide emerged periodically as ocean waters receded to allow passage overland from Asia to America. The migration route into North America ran between glacial ridges to the northeast and southwest, and the first peoples worked their way south along the Canadian Rockies into the American Great Plains and from there to all points of the compass. The migrants came in three waves. The first consisted of what archaeologists call the Amerinds, the ancestors of most Native American peoples and the progenitors of most Native American languages. Second were the Na-Dene, a cultural...