Nova

Megabeasts' Sudden Death

What killed the mastodons? Thirteen thousand years ago, these tusked beasts disappeared from North America, along with some 35 genera of oversized mammals, including woolly mammoths, saber-tooth cats and even camels. For four decades, debate has raged over the cause of this extinction. In LAST EXTINCTION, NOVA presents an exclusive investigation of a startling and controversial new hypothesis which suggests that a cosmic collision could be the culprit. If a comet exploded in the upper atmosphere over the Great Lakes, the blast would have vaporized everything within a 100-mile radius. From coast to coast, wildfires would have raged and turned forests into cinder. Now, at more than two dozen sites across the continent, a multidisciplinary team finds evidence that just such a fire once ravaged North America. But other scholars argue that ancient hunters armed with a distinctive, lethal stone weapon -- the Clovis spear point -- drove the giant beasts into oblivion. Still others believe the unstable climate at the end of the Ice Age was responsible. Now the dramatic new evidence of a cosmic explosion suggests a third possibility -- that mammoths and mastodons already stressed out by human "overkill" and climate change may have received a fiery coup-de-grace as devastation swept across the continent.