Climatological, pedological and faunal investigations conducted in the Upper Midwest and the Ozark Highlands indicate that the environment to which man in the Ozarks was adapting over the past 12,000 years has undergone several major shifts, beginning with a cool-moist boreal forest situation followed by a period of warming and aridness resulting in prairie and deciduous forest climaxes and subsequently, in the last 4000-5000 years, change to the pattern reflected by present conditions.
Cole, Kenneth W.
"Consideration of Macro-Climatic and Macro-Biotic Change in the Ozark Highlands during Post-Glacial Times,"
Journal of the Arkansas Academy of Science: Vol. 25
, Article 8.
Available at: http://scholarworks.uark.edu/jaas/vol25/iss1/8