research

I study how cooperation is organized and sustained in human societies. Specifically, how social influence is distributed, how norms are enforced and transmitted, and how individuals navigate risk through their social relationships. I work at three scales: long-term ethnographic fieldwork in southwest Ethiopia, comparative analysis using global ethnographic databases, and computational modeling. Together these test evolutionary theory against empirical data from culturally diverse, subsistence-based populations.

My research program is organized around four connected questions.

Leadership and coordination

How do communities decide who leads, and what do leaders actually do? My fieldwork among the Chabu and Hamar of southwest Ethiopia, combined with cross-cultural analyses across scores of societies, shows that leadership is neither universal in form nor reducible to a dominance vs. prestige dichotomy. I developed the Multi-Capital Leadership Theory, which treats leadership as grounded in four forms of capital: material, social, somatic, and neural. Different ecologies and group demands favor different capital “portfolios.”

Norms, punishment, and cultural transmission

How are cooperative norms enforced, taught, and stabilized across generations? My comparative work shows that socioecological factors, particularly inequality and economic intensification, predict variation in punishment systems more strongly than shared cultural ancestry. The Leader-Directed Teaching Hypothesis I recently advanced positions community leaders as central agents in transmitting opaque cooperative norms through active teaching. This links social influence to the cultural stability of cooperation.

Social networks and risk buffering

How do individual decisions about relationships scale into the network structures that shape coordination, conflict, and resilience? Through an NSF Human Networks and Data Science grant, I co-direct a multi-site longitudinal study of interethnic networks across four pastoralist communities in Ethiopia’s Omo Valley. Early results show that intercultural and inter-gender ties form even within strongly patriarchal settings, suggesting one way relational structures buffer risk and sustain cooperation under ecological and economic pressure.

Health, ecology, and inequality

How does social position translate into differential health outcomes in communities undergoing rapid socio-economic transition? The Omo Valley Research Project is building a biosocial dataset across the Hamar, Kara, Kwegu, and Nyangatom, linking demographic and economic profiles to anthropometric, cardiometabolic, and functional health measures. Working with Ethiopian epidemiologists and virologists, we are adding biomarkers of stress and immune function to test how market integration, network position, and gendered institutions shape physiological well-being. The work treats social position as a causal mechanism and looks at the bidirectional pathways through which health and social structure shape one another.