Not a new theory, but now with a bit more evidence:

New research suggests toward end of Ice Age, human beings witnessed fires larger than dinosaur killer, thanks to a cosmic impact

There is one bit that has me raising a skeptical eyebrow:

The KU researcher and his colleagues believe the data suggests the disaster was touched off when Earth collided with fragments of a disintegrating comet that was roughly 62 miles in diameter — the remnants of which persist within our solar system to this day.

A 62 mile diameter comet would be many times bigger than the one that whacked the dinosaurs. So *perhaps* they mean that it was 62 miles in diameter before it fragmented, and Earth only hit a fraction of it. On the other hand if it fragments sufficiently, so that the chunks were reduced in size enough that they would all burn up in the atmosphere, there’d be no cratering. The total amount of energy dumped onto Earth might be many times greater than the KT impact, but it would come in the form of a quick flash of light and a series of mighty booms rather than a cratering event throwing gigatons of ash and tectites into the sky.

An important point for future discussions of planetary defense: it’s better to be ht by a cloud of little bits than a single giant impactor, even if the cloud hits with more total energy. The atmosphere serves as a bit like a bulletproof vest for the planet, and if someone if going to shoot you with a 12 gauge while you’re wearing such a vest, you’d rather they shot you with a mass of birdshot than a single deer slug. So arguments that planetary defense strategies should avoid energetic systems like nukes in favor of soft, slow processes like solar sails and gravity tractors and the like because nukes might fragment the impactor… not terribly good arguments.