“About thirty-five genera of mammals disappear from America, about half of them in a brief window of 500 years, 13,200 to 12,700 years ago, with Clovis hunters occupying the core of that time period. A sudden cooling, the Younger Dryas, descends on the Earth by 12,880 years ago, marking the terminal appearance of many of these animals. Suspected causes of the YD are still contentious. But it signals the end of Clovis and much of the megafauna.”