Where does the concept of trust fit into evolutionary theory? The gene selection idea has a disadvantage: it appears unable to explain the altruistic behaviour of certain animals. ‘Evolving trust and cooperation’ looks at possible explanations for this behaviour and applies it to humans. We often face situations in which we must decide whether to help others. Sometimes this decision is based on gain but often the decision is complex. ‘Social dilemmas’ involve decisions in which we consider the overall outcome as well as personal outcomes. Evolutionary psychologists think we can explain at least some aspects of our thinking and behaviour as the result of natural selection.