[meteorite-list] Mammoth-killing comet hypothesis pooped on again

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Tue, 15 Dec 2009 07:09:27 -0500
Message-ID: <dsuei550gecsg9fep79skgsvbb7cf0m8k9_at_4ax.com>

http://www.canada.com/technology/MAMMOTH+DISCOVERY/2340164/story.html

Mammoth discovery: researchers find woolly beasts went extinct slowly
 
By Margaret Munro, Canwest News ServiceDecember 14, 2009

The bones of the woolly mammoth may be spectacular, but scientists say droppings
reveal a more complete story about the shaggy beast's demise.

"Genetic fossils" left by feces and urine show the woolly mammoths grazed along
the Yukon River thousands of years longer than previously believed, an
international team reported Monday.

One of the samples, taken from ancient permafrost, indicates the creatures were
still around as recently as 7,600 to 10,000 years ago.

The findings blow holes in a theory that the mammoths and other ice age
megafauna like sabre-toothed tigers were wiped out when a comet or some sort of
extraterrestrial impact hit the earth 13,000 years ago.

Overkill by early hunters when they arrived in North America or some sort of
"hyperdisease" have also been invoked to try explain the extinctions.

"Our findings suggest that these events, if they occurred as classically
conceived, did not deliver the death blow," the team reports in the Proceedings
of the National Academy of Sciences.

Rather the new evidence points to a slow decline over several thousand years.

"It's provocative, but I think goes a distance to understanding the dynamics of
what happened," says co-author Duane Froese, an earth scientist at the
University of Alberta, who led the team to a well-preserved ancient outcropping
of permafrost on the banks of the Yukon River in Alaska.

The DNA in the permafrost has been frozen in place since it hit the ground and
points to the increasing value of droppings, which are much more plentiful that
bones and fossils.

"An animal leaves only one skeleton," Froese told Canwest News Service on
Monday. But they "shed DNA" throughout their lifetime in their feces and urine.

He says the DNA the team has uncovered in the permafrost gives an intriguing
"snap shot" of when central Alaska and the Yukon was a much drier, colder place.
While covered with trees today, it would have been windswept grassland 10,000
years ago.

And the frozen dirt reveals the region was one of the "ghost ranges" of the
mammoth as the population dwindled away.

DNA from the mammoth and prehistoric horse was found in a permafrost layer that
dates to between 10,500 and 7,600 years ago, which is between 2,600 and 5,600
years after the animals' supposed extinction.

The findings indicate the mammoth and horse coexisted with the first human
immigrants in America for 3,500 years and "were therefore not wiped out by human
beings or natural disasters within a few hundred years, as common theories
otherwise argue," team leader Eske Willerslev of the University of Copenhagen
said in a statement released with the study.
Received on Tue 15 Dec 2009 07:09:27 AM PST