Evaluating the relationships between climate change, population pressure, economic intensification, and childhood stress in the Prehispanic Nasca region of Peru

Abstract

Climate change can adversely affect population health by limiting resource availability. Climate shocks may cause resource shortfalls directly via declining economic productivity, but favorable climate conditions may also create food shortages indirectly by promoting demographic growth that then pressures a resource base. Current population health and capacities for resilience reflect long-term human-environment interactions, highlighting the need for studies on the relationship between climate and population health through time. In this article, we combine theory from population ecology and life history with structural equation models to evaluate archaeological evidence of changing population health in response to climate change in the Nasca highlands of Peru from the terminal Middle Horizon to Late Intermediate period (1250 - 500 cal BP). Specifically, we examine potential causal chains between local precipitation, population growth, agricultural intensification, and two skeletal indicators of childhood physiological stress—cribra orbitalia (CO) and porotic hyperostosis (PH)—in 149 radiocarbon dated individuals. We find that higher precipitation has a positive indirect impact on PH frequency that is entirely mediated by local population pressure and maize agricultural intensification. Precipitation has a negative direct effect on CO, which is most common during intervals of extreme drought, low dietary maize inputs, and in periods of higher fertility. Additionally, we find that PH and CO negatively co-vary over time. These findings add to a growing body of evidence that, though PH and CO have historically been considered manifestations of the same pathological process, these two skeletal lesions likely result from distinct sources of physiological stress in the Prehispanic central Andes.