Devastating comet hit North America 13,000 years ago?

Microscopic diamonds found a few feet underground are evidence that a big destructive comet hit North America 13,000 years ago, scientists say. The LA Times reports:

According to the theory -- which has its critics -- as the comet broke apart, it rained fire over the entire continent, igniting the plains and the forests and creating choking clouds of smoke.

Heat from the explosions and the massive fires melted substantial portions of the Laurentide glacier in Canada, sending waves of water down the Mississippi and into the Gulf of Mexico. That triggered changes in Atlantic Ocean currents, which ushered in a 1,300-year ice age known as the Younger Dryas.

Battered by fire and ice, as many as 35 species of mammals, including American camels, the short-faced bear, the giant beaver, the dire wolf and the American lion, either immediately vanished or were so depleted in number that humans hunted them to extinction.

The humans, a Paleo-Indian grouping known as the Clovis culture for the distinctive spear points they employed, suffered a major population drop, disappearing in many areas for hundreds of years.

(PDF article about the Clovis Comet)