That’s Joe Katzman’s comment at this interesting post by Donald Sensing on a major asteroid impact in North America thirteen thousand years ago.

…the worst consequence of the cataclysm was the mass extinctions of the late Pleistocene that have heretofore been attributed to overhunting by the Clovis peoples of the continent. The extinctions were additionally blamed on the Younger Dryas. The new impact theory, though, says that the comet’s multiple explosions (caused by its breakup in the high atmosphere) themselves caused the extinctions: “at least 35 genera of the continent’s mammals went extinct