Mammoth extinction: the smoking gun?

At a meeting of the American Geophysical Union, scientists offered new evidence that not only man, but nature, had a hand in the rapid decline of the mammoth and other North American megafauna. Eight 35,000-year-old mammoth tusks show damage apparently due to being peppered with tiny fragments of metal (mainly iron and nickel) moving at very high speed. All the impacts were from one direction. Richard Firestone from the Lawrence Berkeley National Laboratory said, "We think that there was probably an impact which exploded in the air that sent these particles flying into the animals."