New evidence suggests the first Americans may have come from Europe, not Siberia:
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 the mastodon relic found near the mouth of the Chesapeake Bay turned out to be 22,000 years old, suggesting that the blade was just as ancient.
Whoever fashioned that blade was not supposed to be here.
Fascinating story.
(Via Tyler Cowen.)