New investigation questions drought as cause for the exodus of Cahokia
Cahokia Mounds, once a thriving settlement near present-day St. Louis with a population of around 50,000 people, experienced a mysterious decline around 1400. While it has been widely assumed that a severe drought and subsequent crop failure led to the mass departure of Cahokians, a recent study conducted by Natalie Mueller, assistant professor of archaeology at Washington University in St. Louis, and Caitlin Rankin, Ph.D. '20, challenges this theory.
In their study published in The Holocene, Rankin conducted extensive soil analysis at the Cahokia site to examine the isotopes of carbon present. By studying the carbon signatures left by plants during the period of population collapse and widespread drought across the Midwest, the researchers aimed to unravel the causes behind the settlement's abandonment.
Through their analysis, the researchers discovered that while plants adapted to dry climates, including prairie grasses and maize, did incorporate distinctive carbon signatures, the majority of other food sources, such as squash, goosefoot, and sumpweed, showed no significant changes in carbon ratios. This suggests that no wholesale shift in plant types occurred during the critical period, representing a lack of evidence for widespread crop failure.
Mueller and Rankin propose that the Cahokians had advanced engineering and irrigation systems, allowing them to sustain their crops even under challenging climatic conditions. Moreover, their organized society likely possessed effective systems for grain and food storage. With available resources, a diverse diet that included animals and forest produce, and potential adaptation to climate change, it is plausible that the inhabitants did not feel the full impact of the presumed drought.
To gain further insights into the diets and agricultural practices of Indigenous people in the Midwest, Mueller plans to develop a comprehensive database of paleo-botanical evidence from the region. Additionally, she intends to conduct controlled cultivation experiments on campus, simulating ancient droughts and studying the response of specific food crops.
Rather than envisioning a sudden mass exodus, Mueller suggests that the gradual movement of people, seeking kin or new opportunities, may have spurred the dispersion of the Cahokians. External pressures likely played a role, though the exact circumstances remain intricate and require further exploration.
The new study challenges the prevailing notion of the Cahokia exodus being solely driven by drought. This refocuses the archaeological discourse on possible alternative factors contributing to the decline of this once-flourishing community. By unraveling the complexities surrounding Cahokia's abandonment, we inch closer to a clearer understanding of the ancient past and the choices made by its inhabitants.