Do humans have psychological adaptations for thinking about ethnic social categories? How do cultural evolutionary processes shape these boundaries? I conduct cross-cultural and developmental research, particularly among agro-pastoralists in the Peruvian altiplano along the Quechua-Aymara linguistic border to address this question. 

Why and how do family members affect fertility across space and time? I use demographic methods and modelling to understand social influences on reproductive decisions and how these can give rise to puzzling phenomena such as the demographic transition, below replacement fertility, and cross-site variation in life history decisions.

Why do people adopt new religious beliefs? Why do others resist? Why do some pilgrimage sites become popular while others disappear? I am studying the emergence and spread of a new religious ritual site in the Peruvian Altiplano to understand social transmission in humans, and our motivations for engaging in seemingly non-functional behaviors.