Science Daily 7/3/08:

"Exploding Asteroid Theory Strengthened By New Evidence Located In Ohio,
Indiana"

"Geological evidence found in Ohio and Indiana in recent weeks is
strengthening the case to attribute what happened 12,900 years ago in North
America -- when the end of the last Ice Age unexpectedly turned into a phase
of extinction for animals and humans ­ to a cataclysmic comet or asteroid
explosion over top of Canada."

[snip]

"The timing attached to this theory of about 12,900 years ago is consistent
with the known disappearances in North America of the wooly mammoth
population and the first distinct human society to inhabit the continent,
known as the Clovis civilization. At that time, climatic history suggests
the Ice Age should have been drawing to a close, but a rapid change known as
the Younger Dryas event, instead ushered in another 1,300 years of glacial
conditions. A cataclysmic explosion consistent with West¹s theory would have
the potential to create the kind of atmospheric turmoil necessary to produce
such conditions."

Full article here:

http://www.sciencedaily.com/releases/2008/07/080702160950.htm