Paleoindian groups occupied North America throughout the Younger Dryas interval, which saw a rapid return to glacial conditions approximately 11,000 years ago. Until now, it has been assumed that cooling temperatures and their impact on communities posed significant adaptive challenges to those groups. David Meltzer from the Southern Methodist University in Dallas, USA, and Vance Holliday from the University of Arizona in Tucson, USA, suggest otherwise in their review of climatic and environmental records from this time period in continental North America.
     From their analysis, they conclude that on the Great Plains and in the Rocky Mountains, conditions were in reality less extreme and therefore may not have measurably added to the challenge routinely faced by Paleoindian groups, who during this interval, successfully dispersed across the diverse habitats of Late Glacial North America. Meltzer and Holliday question whether the impact of cooling on Pleistocene North Americans was actually that pronounced or widespread and, if it was, whether it was similarly abrupt and severe, and in the same direction, across North America. Their comprehensive review of the climate and environment of North America during that time and its possible impact suggests that the Young Dryas age cooling was not as sudden, extensive, or severe as has previously been suggested and the notion that these conditions may have taken the Paleoindians by surprise is questionable.
     The authors conclude: "All things considered, it is likely that across most of North America, south of the retreating ice sheets, Paleoindians were not constantly scrambling to keep up with Younger Dryas age climate changes. After all, adapting to changing climatic and environmental conditions was nothing new to them - it was what they did."

Source: Springer (12 April 2010)