Transitions in the longue durée

People involved: Stefani Crabtree

Keywordsarchaeology, food webs, agent-based modeling, climate change, human/environment interaction

Project Description

The Anthropocene, “a human-dominated geological epoch”, implies a fundamentally new dynamic between humans and environments. As global populations expand, and with an eye to planning for the future, we must enhance our understanding of how and when humans most dramatically altered their environments in the past, and the ways in which these changes have compounding consequences. My research in archaeoecology examines the impacts of humans on past environments and how ecosystems influenced past societies. By studying archaeological cases where we know that local extinctions occurred, examining when, where, and how regime shifts happened, we can calibrate our understanding of human-environment interaction to help predict future ecosystem destabilization.


In my work I combine food web compilation and analysis with agent-based modeling to examine how people modified past landscapes. One of the groups I have studied, the Ancestral Puebloans in the American Southwest, completely abandoned the region in the late A.D. 1200s. This abandonment has long puzzled archaeologists; my work suggests that the accumulation of small choices, such as intensifying maize farming, decreased the resilience of the greater ecosystem. When external shocks occurred in the mid to late A.D. 1200s, including poor productive conditions relative to population growth followed by a prolonged drought, the greater ecosystem was so significantly altered that Puebloans were left vulnerable to famine.


Agent-based models (ABMs) model the actions and interactions of individuals in a defined environment, creating societies in silico for testing hypotheses, and have been instrumental in identifying causes of resource depression worldwide. Food webs, ecological networks of who eats whom in an ecosystem, allow examination of how species relate to other species, and provide a quantitative framework for assessing extinctions resulting from species loss or invasion. These approaches are well-suited to archaeological data, which scales from site- and midden-level analysis to regional patterns.


I have been publishing on the food web and ecosystem of the Puebloans, and have begun compiling data on several other societies worldwide, including Australian Aboriginal people, Bronze Age Mongolia, and the LBK culture in Neolithic central Europe. I propose to spend my time at CRI examining how external environmental pressures coupled with decisions by individuals within societies can lead to destabilization (in the Pueblo case), to coevolution and stability (Australian Aboriginal case), and transitions in human adaptation (LBK and Mongolia). These models can then be used as calibration for understanding our trajectory as a species.