Bernard Wallner is professor of comparative anthropology at the Department of Behavioural Biology and adjunct professor at the Department of Anthropology, University of Vienna, Austria. His research is concentrated on individual stress reactions effected by environmental and social stressors. Physiological stress is analyzed on behavioral, physiological respectively endocrine and molecular biological levels in humans, monkeys, and rodents. Bernard is a founding member of the Austrian Research Center of Primatology and a member of the New York Academy of Sciences. He teaches courses in primatology and comparative anthropology and earned his PhD in Behavioral Endocrinology.

Christopher Boehm argues human social rank has evolved in the rain forest. In such an environment, our human-like ancestors may have developed egalitarian communities comparable to recent indigenous populations.

However, in the course of human evolution, social systems have changed in relation to population growth from small egalitarian groups to chiefdoms tribes and recent large-scale populations living in democratic or autocratic states. Parallel to the development of divers' human social systems prosocial behaviors such as cooperation, empathy, or coalition-forming became typical human traits of interactions. Sharing these behaviors caused social cohesion within groups resulting in better individual reproductive success. Due to that, a game theoretic approach has contributed to a better understanding of these behaviors in relation to human evolution. The universality of prosocial behaviors may underline the assumption that it origins from an evolutionary development. Irrespective of different societies or ecological adaptation, all human social communities do share the same characteristics of cooperative behaviors, namely altruism, direct and indirect reciprocity and punishment of free riders who do not reciprocate prosocial behavior. However, most studies do not consider the social rank positions between prosocial interacting individuals. For example, cooperative behavior between individuals of different rank positions is common in the academic field or between employees in companies. According to our evolutionary heritage this presentation will highlight the effects social rank on cooperation or fairness but also on its defection in relation to stress physiology.