More evidence that humans were in North America over 20k years ago

Dr. John Speth (University of Michigan, Ann Arbor), who also excavates at White Sands, used to half-joke that the people here during the glaciation must have made all of their tools out of ice. He was confident North America was inhabited for longer than it was then believed (~13,000 years). But aside from the coastal sites that would now be underwater (sea level rose as the glaciers melted), all the inland tools appear to have melted away.