Cooperative behaviour is widespread among individuals at all levels of biological organisation. This poses a problem to traditional views of natural selection, which predicts that individuals should behave selfishly. While much work has been done to resolve the problem of cooperation, recent advances in theoretical and empirical studies made clear that very important questions regarding the general understanding of cooperation are still unresolved. Our integrative ProDoc program will take advantage of the diversity in study systems and conceptual approaches of participating PIs and Co-PIs. The research modules will involve mathematical modelling and empirical research to determine the mechanisms of cooperation at the levels of genes, physiology, ecology and cognition. With the combined expertise of the involved PIs and Co-PIs and the diversity of research approaches pursued in the different modules, we can offer the participating PhD students an outstanding, world-class education and research environment, which will facilitate their development as independent and internationally highly qualified researchers. This ProDoc program will train a critical mass of young researchers to initiate future research programmes bridging across different fields of evolutionary biology.