The central Illinois River valley was the setting for two significant cultural changes during late prehistoric period (A.D. 250 to A.D. 1,450). As presumed gains in population growth taxed the pre-existing subsistence system that included indigenous cultigens, the first change ca. A.D. 1,050/1,100 involved the intensification of food production vis-à-vis maize agriculture and the adoption of Mississippian lifeways by Late Woodland peoples native to the valley. A series of Mississippian centers emerged and subsequently waxed and waned in influence over the ensuing two to three centuries. The second cultural change around A.D. 1300 is marked by an increase in interpersonal violence and warfare as an Oneota population encroached on Mississippian-occupied territories. Reasonably large, well-preserved skeletal samples provide a means to assess demographic and epidemiological variability during these periods of significant sociocultural change and interaction. The re-analysis of the multi-component skeletal sample from Dickson Mounds, which includes a reassessment of the mound and burial chronology, provides a fresh perspective on the evolution “health” and demographic patterns in west-central Illinois.
A total of 2,271 skeletons were analyzed during the course of research. This includes the Late Woodland, Mississippian, and/or Oneota-affiliated skeletal samples from Dickson Mounds (n = 861), the Morton Complex (n = 209), Orendorf (n = 268), Crable (n = 172), and Norris Farms 36 (n = 296). The first component of the research involved paleodemographic analyses of fertility and population growth, childhood survivorship, and adult mortality. Based on the proportion of juvenile skeletons in each of the diachronic skeletal samples, the entire late prehistoric period can be characterized by relatively high fertility levels. Elevated levels of early childhood mortality were also characteristic of the entire time period in question. Employing a recently developed maximum likelihood method of estimating age-at-death for adults (Transition Analysis; Boldsen et al., 2002), hazard model analyses reveal that the patterns of survivorship are significantly different from abridged life tables previously published for the region. Individual estimates of age-at-death and the cumulative hazard functions point toward individuals living longer than previously estimated. The development of Mississippian-era palisaded towns was particularly detrimental to young adult female survivorship. High fertility rates and stages of population growth were offset by a high risk of death for women during their early fertile years and a generally lower adult life expectancy for males. These findings support the notion that a high-pressure system of elevated fertility and mortality existed among late prehistoric populations of the Midwest, comparable to and parsimonious with the demographic regimes observed in extant, traditional populations.
The second component of the research was a paleoepidemiological analysis explicitly designed to detect heterogeneity in frailty and selective mortality. Indicators of childhood growth and stress were shown to have a variable impact and association with mortality patterns through each of the diachronic phases and by sex. These findings argue against the applicability of childhood growth and stress indicators as universal measures of “health” or as elements of indices designed to demonstrated broad meta-analytic patterns dependent upon skeletal samples subject to varying population dynamics. The measures of dental health displayed remarkable consistency with the adult mortality patterns. Across the diachronic phases, young adult females were found to have elevated rates of carious lesion development and progression that indicate variable levels of frailty and selective mortality existed in late prehistoric societies of the Midwest. By contrast, females that survived into their post-reproductive lifespan can be characterized by good dental health that included few carious lesions and lower rates of attrition. Dental health patterns for males across the diachronic phases were age-progressive. The probability of carious lesion development and progression, advanced attrition, abscesses, and ante-mortem tooth loss increased with age-at-death. These models parallel the male attritional mortality profiles and demonstrate that traditional paleopathological indicators must be considered as part of larger population processes. These findings echo and provide evidence for the concerns originally synthesized in the “Osteological Paradox” (Wood et al., 1992a).
This research was supported by dissertation improvement grants from the National Science (BCS-0751484) and the Wenner-Gren Foundations, and travel grants from the Max Planck Institute for Demographic Research.