Did a comet wipe out North American mammals?

I read this New Scientist article with great interest, as I have always maintained that the most likely cause of the 10,000BC North American cataclysm was a pole shift. To me that was far more likely than "the Indians killed 22 million animals for food" theory.

New evidence shows that the cause may have been a comet:

Citing several lines of evidence, the team suggests that a wayward comet hurtled into Earth's atmosphere around 12,900 years ago, fractured into pieces and exploded in giant fireballs.

...immense wildfires scorched North America in the aftermath, killing large populations of mammals and bringing an abrupt end to the Clovis culture. "The entire continent was on fire,"

... the evidence lies in a narrow 12,900-year-old carbon-rich layer of sediment found at eight well-dated Clovis-era sites and a peppering of sediment cores across North America, as well as one site in Belgium.

In this layer the team detected several different types of extraterrestrial debris, including nanodiamonds that are only ever found on Earth in meteorites; tiny carbon spherules that form when molten droplets cool rapidly in air; and cage-like carbon molecules containing the rare isotope helium-3, far more abundant in the cosmos than on Earth.

According to one website, nanodiamonds can be found "in meteorites, protoplanetary nebulae, and interplanetary dust." Other hints that it may not necessary arrive on earth via a comet are:

"it is unclear what fraction of the nanodiamond population is actually associated with supernovae" (found here)

"An astrophysicist from Lawrence Livermore National Laboratory's Institute for Geophysics and Planetary Physics has found that some nanodiamonds, the most famous and exotic form of stardust, may instead have formed within the inner solar system." (found here)

Interestingly, the same scientists were previously promoting a supernova as the orginal cause (see my blog entry), and this is not mentioned at all in the New Scientist article! Could it be a conspiracy.....