Who were the first Americans, and when did they arrive? Did they get here by land or sea? Did a single group populate the continent, or did many? Exciting recent finds at sites have triggered new theories. Alan Alda tries to find out who's saying what, and why.

Who were the first Americans, and when did they arrive? Did they get here by land or sea? Did a single group populate the continent, or did many? Exciting recent finds at sites have triggered new theories. Alan Alda tries to find out who's saying what, and why.