13.11.2025 Carsten de Dreus

Among the major transitions in the evolution of biological complexity is the clustering of independent individuals in groups, colonies and societies. Clustering allows for individuals to cooperate – paying costs to benefit others’ fitness – and to compete – spending ‘…energies on injuring others, and on protecting against being injured'. Somewhat puzzling is that throughout nature, cooperating and competing can co-occur, with individuals paying costs to both increase and reduce another’s fitness. In this talk I show how such co-occurrence of cooperation and competition, while robustly observed, escapes prevailing theory on cooperation, and on animal contests and competition. Next I show, with evolutionary game theory and numerical simulations, when and how strategies combining cooperation and competition become prevalent and evolutionary stable in both unstructured populations and structured populations with varying levels of inter-community interactions. Among our results is that, as interactions within communities become comparatively productive, individual fitness benefits from heretofore unidentified strategies that combine parochial cooperation (cooperate within but not between groups) and neighbour nastiness (compete within but not between groups). Results integrate prevailing theory and observation on cooperation with models of animal contests and competition, resonate with recent empirical observations, and suggest that individual fitness in group-forming species in the ultimate depends on evolved capacity to flexibly decide whether, when, and with whom to cooperate and compete.