Did asteroid wipe out America's first people?

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Did asteroid wipe out America's first people?
New evidence suggests extraterrestrial cause for disappearance of Clovis culture
mongabay.com
May 17, 2007

An asteroid may have caused the near-extinction of North America's first humans, argues a series of studies to be presented May 24, at the American Geophysical Union's meeting in Acapulco, Mexico. Nature reports that while the theory has been discounted in the past, new research suggests that an comet or asteroid could have exploded above or on the northern ice cap some 13,000 years ago, plunging regional temperatures to plunge for the next 1000 years. The theory would also help explain the disappearance of the continent's large mammals, including woolly mammoths, American lions, and the saber tooth tiger.

"The magnitude of this discovery is so important," Nature quotes James Kennett, a palaeoceanographer at the University of California, Santa Barbara (UCSB), as saying. "It explains three of the highest-debated controversies of recent decades."

The article says that the presentations will certainly be controversial since leading hypotheses already explain various occurrences during the period.

"A change in ocean circulation is generally thought to have brought about the onset of the millennium-long cooling, which is known as the Younger Dryas. This cooling might, in turn, have caused the Clovis hunters to disappear. And, if they had not previously been killed by disease or hunted to extinction, the big prehistoric beasts may also have been doomed by this change in climate," writes Rex Dalton, author of the Nature article.

The new evidence for the cosmic turn of events "comes in the form of geochemical analysis of sedimentary layers at 25 archaeological sites across North America - 9 of them Clovis," Dalton continues. "Certain features of the layers, say the team, suggest that they contain debris formed by an extraterrestrial impact. These include spherules of glass and carbon, and amounts of the element iridium said to be too high to have originated on Earth. In addition, the rocks contain black layers of carbonized material, which the team says are the remains of wildfires that swept across the continent after the impact."

CITATION: Rex Dalton. (2007) Blast in the past? Nature MAY 16, 2007

This article is based on a news release from the University of East Anglia

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