Comets Over Canada...Maybe Not!

Re. the Younger Dryas Impact theory.

Since layers of charcoal in the fossil record exist in Northern Europe from around the onset of the Younger Dryas, and since this charcoal can be explained as a result of trees killed by the onset of cooler temperatures serving as fuel for wide-spread forest fires, there is no reason to postulate an "explosion of extra-terrestrial material over northern North America" to account for a similar charcoal layer in North America.

H/T Jeff Hecht, who has a story on the impact theory in last week's New Scientist (from which I have copped, hopefully legally, the picture above-left).