http://www.sfgate.com/cgi-bin/article.cgi?f=/chronicle/a/2003/07/25/MN253509.DTLAn archaeological site in Siberia -- long thought to be the original jumping-off point for crossing the Bering land bridge into North America -- is actually much younger than previously believed, shaking the theory that the first Americans migrated overland during the final cold snap of the last great ice age.
Using radiocarbon dating, scientists found that the Ushki site, the remains of a community of hunters clustered around Ushki Lake in northeastern Russia, appears to be only about 13,000 years old -- 4,000 years younger than originally thought.