Saturday, May 24, 2008

Did Comets Cause Ancient American Extinctions?

Anne Casselman
for National Geographic News
May 6, 2008

Debate has heated up over a controversial theory that suggests huge comet impacts wiped out North America's large mammals nearly 13,000 years ago.

The hypothesis, first presented in May 2007, proposes that an onslaught of extraterrestrial bodies caused the mass extinction known as the Younger Dryas event and triggered a period of climatic cooling.

The theory has been debated widely since it was introduced, but it drew new scrutiny in March at the annual meeting of the Society for American Archaeology annual meeting in Vancouver, Canada.

Stuart Fiedel from the Louis Berger Group, a private archaeological firm in Richmond, Virginia, argued that the theory fails to address some major questions—like how comet blasts could have wiped out woolly mammoths and saber-toothed cats in North America Also around this time, large mammals including mammoths, mastodons, horses, camels, and saber-toothed cats went extinct in North America. Previous hypotheses have suggested that early humans wiped out the large animals in a prolonged act of slaughter referred to by scientists as overkill.