War exacts a great social cost, not only upon its direct participants, but also upon the lives of the friends, family, and community of those who experience it. This cost is particularly evident in the increased frequencies of aggressive behaviors, including homicide, assault, and domestic violence, enacted by Western military veterans with posttraumatic stress disorder (PTSD). Similarly, among contemporary non-Westernized peoples, a cross-cultural conducted by Ember and Ember (1994) found a relationship between war and various forms of intragroup violence, including domestic violence, assaults, homicides, and violent sports. It is unknown, however, if this positive association between warfare and intragroup violence extends longitudinally for prehistoric populations uninfluenced by modern states.

To test Ember and Ember’s (1994) results in an archaeological culture, this study examines whether or not an association between war and intragroup violence was present during the Mississippian Period (ca. AD 1000-1450) of the Central Illinois Valley (CIV). The Mississippian Period of the CIV represents an ideal context for examining war and violence questions, as considerable evidence of war and violence has been amassed from archaeological and bioarchaeological analyses. High rates of skeletal trauma, fortification construction, and the placement of habitations sites in defendable areas indicate war was of particular concern during this period. Yet, little is known regarding the diachronic and synchronic variation in violence in this region.

In this research, skeletal remains representing 776 individuals from five CIV sites (Dickson Mounds, Larson, Berry, Crable, and Emmons) were analyzed for violence-related skeletal trauma, biodistance, and mortuary data. From the aggregation of these data, two models of intergroup violence and two models of intragroup violence were explored. The intergroup models examined were: 1) warfare victims from the local community and 2) warfare captives. The intragroup models assessed include: 1) domestic violence and 2) male-male fights. Results support the hypothesis that as intergroup violence increased during the Mississippian Period in the CIV, intragroup violence increased concomitantly. While warfare and intragroup violence occurred in low frequencies early in the Mississippian Period, after AD 1200, both intragroup and intergroup violence were likely endemic.