 The first debate between proponents and skeptics was held at the 2008 Pecos Conference in Flagstaff, Arizona.In 2009, a paper in the "Proceedings of the National Academy of Sciences" offered evidence of impact glass that resulted from the impact of a meteorite.Another asserted that a swarm of carbonaceous chondrites or comet fragments from air burst(s) or impact(s) set parts of North America on fire, caused the extinction of most of the megafauna in North America, and led to the demise of the Clovis culture.