UA professor Vance Holliday and his colleague have put another nail in the coffin for the hypothesis that an extraterrestrial impact at about 12,900 ybp in North America produced the end of the Younger Dryas climate and the Clovis culture. [right, a Clovis spear point can be seen in the center of the photo, lodged in the skeleton of a mammoth excavated by UA archaeologist Emil W. Haury at Naco, Ariz., in 1952. Credit, Arizona State Museum]In an article in the current issue of Current Anthropology uses radiocarbon dates, geomorphological and archeological evidence to conclude that "an extraterrestrial impact is an unnecessary solution for an archaeological problem that does not exist."
A spate of recent studies have disproved evidence of the impact itself.
Ref: The 12.9-ka ET Impact Hypothesis and North American Paleoindians, Vance T. Holliday and David J. Meltzer, DOI: 10.1086/656015