[The cosmic impact that started the Younger Dryas] marked the end of their story, and the end of an epoch, really. There's not a single Clovis point found anywhere in North America that's above that black mat. They're all in it or below it. And there's not a single mammoth skeleton anywhere in North America that's above it. A huge part of the die-off could have been as a direct result of the impacts themselves, but impacts and airbursts south of the ice cap, particularly as far south as New Mexico, would also have set off wildfires. There's overwhelming evidence that gigantic wildfires raged at the onset of the Younger Dryas--in fact, more soot has been found at the Younger Dryas Boundary than at the Cretaceous-Paleogene Boundary. We did the calculations and it looks like as much as 25 percent of the edible biomass and around 9 percent of the total biomass of the planet was on fire and destroyed within days or weeks of the YDB. So in many areas if the animals weren't killed outright they wouldn't have been able to forage enough food afterwards to survive. The grass would have burned up, leaves on trees were gone. ... And you know, the other thing is that when comet fragments come in they're traveling incredibly fast and they literally punch a hole in the atmosphere. They actually push the air aside and they bring in that super cold from space, and when they explode in the air that cold plume continues to the ground and you literally have things frozen in place if they were close enough to where the plume came down. It's possible they were fried and then frozen all within a matter of seconds.