Resource scarcity drives lethal aggression among prehistoric hunter-gatherers in central California

Abstract

The origin of human violence and warfare is controversial, and some scholars contend that intergroup conflict was rare until the emergence of sedentary foraging and complex sociopolitical organization, whereas others assert that violence was common and of considerable antiquity among small-scale societies. Here we consider two alternative explanations for the evolution of human violence: (i) individuals resort to violence when benefits outweigh potential costs, which is likely in resource poor environments, or (ii) participation in violence increases when there is coercion from leaders in complex societies leading to group level benefits. To test these hypotheses, we evaluate the relative importance of resource scarcity vs. sociopolitical complexity by evaluating spatial variation in three macro datasets from central California: (i) an extensive bioarchaeological record dating from 1,530 to 230 cal BP recording rates of blunt and sharp force skeletal trauma on thousands of burials, (ii) quantitative scores of sociopolitical complexity recorded ethnographically, and (iii) mean net primary productivity (NPP) from a remotely sensed global dataset. Results reveal that sharp force trauma, the most common form of violence in the record, is better predicted by resource scarcity than relative sociopolitical complexity. Blunt force cranial trauma shows no correlation with NPP or political complexity and may reflect a different form of close contact violence. This study provides no support for the position that violence originated with the development of more complex hunter-gatherer adaptations in the fairly recent past. Instead, findings show that individuals are prone to violence in times and places of resource scarcity.warfare | prehistoric violence | North America

Large-scale effects of migration and conflict in pre-agricultural groups: Insights from a dynamic model

“…In particular, our results are consistent with recent findings showing that reduced environmental productivity is a strong predictor of lethal aggression among prehistoric groups in Central California [24]. …”

Pacifying Hunter-Gatherers

“…The important edited volume by Allen and Jones (2014) provides archaeological surveys and case studies of intense warfare among North American and Australian hunter-gatherers in the absence of contact with agriculturalists (see also Lambert 2002 for a classic survey of North America). Research on Californian hunter-gatherers is of particular significance because of the tremendous amount of skeletal evidence of lethal trauma in areas far from agricultural centers (Allen et al 2016). And in Australia, archaeological evidence as well as historical and ethnohistoric evidence document frequent warfare from ecologically rich drainages such as the Murray River as well as resource-poor desert areas as well (Allen 2014b).…”

Warfare in an evolutionary perspective

“…In a sample of 19 hunter‐gatherer societies, Kelly found a positive correlation between the occurrence of war and population pressure, as measured by how much food is available per person. Moreover, Allen et al found that lethal violence was significantly and better predicted by resource scarcity than by socio‐political complexity (a proxy of the extent to which leaders can coerce their subordinates to go to war), using archeological data on hunter‐gatherer societies in Central California. Finally, it has been proposed that lethal aggression in humans became more frequent in the last 15,000–8,000 year BP (but see Reference ), when population density increased, groups settled down near resource‐rich locations (e.g., river estuaries) and started monopolizing those locations …”