Archaeologists have long held that North America remained unpopulated until about 15,000 years ago, when Siberian people walked or boated into Alaska and then moved down the West Coast.

But a dark, tapered stone blade, nearly eight inches long and still sharp, found near the mouth of the Chesapeake Bay, turned out to be 22,000 years old, suggesting that its makers probably paddled from Europe and arrived in America thousands of years ahead of the western migration.

(READ the story in the Washington Post)