My research revolves around the central theme of social complexity in birds and mammals, which I have studied from many different angles including behavior, cognition, acoustics, and physiology. In recent years my focus has been on quantitative genetics to disentangle environmental, parental and genetic sources of variation in social behavior. My current research aim is to study the evolutionary ecology of social behavior in primates from a quantitative genetic perspective. The rhesus macaques of Cayo Santiago provide the rare opportunity to address quantitative genetic questions about social life in free-living animals thanks to long-term data on parentage and individual life histories. Using so called "animal models", I will analyze these long-term data to determine to what extent mothers and fathers influence their offspring's behavior, either directly or through their genes. I am further interested in assessing the evolutionary potential of social behavior in rhesus macaques by relating genetic variation to fitness.