In a CDDRL research seminar series talk, FSI Senior Fellow Alberto Díaz-Cayeros presented his research on “Epidemiological Shocks, Governance, and Extraction in Colonial Mexico.”

The European conquest of the Americas brought dramatic changes to Indigenous societies, dismantling pre-colonial empires and city-states while imposing exploitative colonial systems. One such institution was the Encomienda, which placed Indigenous communities under the control of individual conquistadores. This system disrupted traditional authority, exploited indigenous labor, and deepened social and economic upheavals. Díaz-Cayeros’s study focuses on Tepetlaoztoc, a city-state in the Acolhua Kingdom of the Aztec Empire, to understand how demographic collapse, epidemic disease, and colonial rent extraction were interconnected.

The research challenges the widely accepted "virgin soil" hypothesis, which attributes the catastrophic population decline — over 90% — to Indigenous Peoples’ lack of immunity to European diseases. Instead, Díaz-Cayeros argues that colonial exploitation and the destruction of political autonomy played a significant role in amplifying the effects of these epidemics. This reframe shifts the narrative from viewing these declines as natural consequences of disease to seeing them as direct outcomes of systemic colonial policies.

Using historical records, Díaz-Cayeros’ study reconstructs population changes in Tepetlaoztoc and employs epidemiological models to analyze how diseases spread and killed so many. For instance, mortality rates during smallpox outbreaks were around 25%, while cocoliztli — a deadly hemorrhagic fever — caused up to 40% mortality. These rates varied depending on social factors, such as land ownership and class. Wealthier or more socially connected groups sometimes fared better, while laborers and marginalized groups were more vulnerable due to overwork and poor living conditions under colonial rule.

The study also employs advanced epidemiological modeling techniques to understand the spread of diseases. These models reveal that the devastation in Tepetlaoztoc was not solely due to pathogens but also to the breakdown of traditional agricultural systems and trade networks. The shift in land use toward livestock farming, for example, disrupted local food production and made recovery nearly impossible. This prolonged what the study calls a “poverty trap,” where the region remained economically and socially stagnant for centuries.

Importantly, the research highlights Indigenous resilience. Codices (historical documents) and oral histories show that indigenous communities actively responded to these crises, storing food and reorganizing resources to survive famine and disease. These accounts challenge the Eurocentric portrayal of Indigenous Peoples as passive victims and instead emphasize their adaptability and agency.

Díaz-Cayeros’ research provides a nuanced understanding of the catastrophic demographic changes in colonial Mexico. It shows that these were not inevitable consequences of disease but were exacerbated by colonial systems that exploited and dismantled Indigenous societies. By combining historical data with modern analytical tools, the study highlights the enduring impacts of colonialism and underscores the importance of including indigenous perspectives in understanding history.

You can view a complete recording of Díaz-Cayeros’ presentation below: