My research interests include the evolution of cooperation, the geography of trust, and human diet and health. In the area of cooperation, I considered the question of why cooperation is very rare in the animal kingdom. My work, published in the Journal of Theoretical Biology, suggests that the fundamental problem with animal cooperation is that it invariably breaks down in the earliest stages. In the area of trust, I considered the question of why some countries are more trusting than others in a paper published in Cross-Cultural Research. In the area of diet and health, I looked at the relationships between food, lifestyle, and health by examining the evolution of the human diet. My book on this topic was published by Picador USA and HarperCollins Canada. I recently discussed the allure of pho (Vietnamese noodles) in the Ottawa Citizen.