His primary research interests include the evolutionary ecology of human reproductive strategies, sexual division of labor, life history, and resource acquisition. He has worked among the Ache of Paraguay and Hiwi of Venezuela as well as the Machiguenga and Yora of Peru. He is currently writing a demography of the Ache foragers. Recent publications include “The Evolution of Premature Reproductive Senescence and Menopause in Human Females” with A. Magdalena Hurtado (Human Nature 2(4):313–350, 1991).