Late Precolumbian Subsistence Change, Socio-political Transformation, and Ethnogenesis 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 and Mississippian 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, these highly mobile family-sized horticultural bands had transformed into settled villagers who practiced full-time maize agriculture, and buried their dead in large communal mounded cemeteries. The period between the 11th and the 15th century is a time of considerable climatic 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.