Late Pre-contact Ethnogenesis, Resilience, and Movement in the Face of Climate Variation in the Upper Illinois River Valley

Post-AD 1000 was a time of tremendous change in the Upper Illinois River valley. The Terminal Late Woodland groups in the region were bordered on the south by emergent Mississippian petty chiefdoms of the Central Illinois River valley, on the north by Oneota societies, and on the east by Fort Ancient groups. Coinciding with this cultural mix was the recent adoption of maize agriculture. First evident isotopically at ca. AD 900, maize became a substantial constituent of Upper Mississippian diet by AD 1100. Archaeologists have proposed that pressure from surrounding groups, including increased violence and intermittent raiding, may have propelled changes in the lifestyle of Terminal Late Woodland people. By AD 1100, numerous groups of full-time maize agriculturalists inhabited the area, some indigneous and some intrusive. The period between the eleventh and the fifteenth century is a time of considerable climatic social fluctuation in this area, that likely contributed to social and subsistence stressors facing these Upper Mississippian societies. In this paper we examine the interrelationships of changes in settlement patterns, diet, and culture, within the context of known climate changes and find that multiple variables, such as violence, migration, and local environmental variability, need to be considered as important potential causal factors in conjunction with regional climate variation.