These general dates coincide with the cold spell—if a “spell” can be said to last for millennia—of the Pleistocene Ice Age. The massive ice sheets that draped across the northern parts of North America and Asia locked up great quantities of the earth’s water. With so much water trapped as ice, the sea levels dropped at least 250 feet and perhaps as much as 350 feet below contemporary levels. Much of the world’s continental shelves were exposed, including a wide swath of land that in effect joined North America and Asia. Long called the Bering Land Bridge, this “bridge” was in fact over 1,000
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