Did a Comet Cause a North American Die-Off around 13,000 Years Ago?

Did a Comet Cause a North American Die-Off around 13,000 Years Ago?: Scientific American: "Today, in Proceedings of the National Academy of Sciences, the same team reports on shock-synthesized hexagonal diamonds, known only from meteorite and other impact events, in a soot layer from Arlington Canyon on Santa Rosa Island in California. The canyon is famous for containing the earliest human remains in North America, dating back to 13,000 years, and the soot layer coincides with the disappearance of the pygmy mammoth from the island."