Evolutionary moral psychology: Lessons from Westermarck

Edward Westermarck, a pioneer of modern evolutionary approaches to human behavior, is best known for his work on incest avoidance, while other significant aspects of his legacy remain unappreciated. This article argues that Westermarck's theory of moral emotions—arguably the most comprehensive evolutionary account of morality to date—offers a valuable analytical framework for investigating the emotional and evolutionary origins of moral judgments. It presents a concise synthesis of Westermarck's core ideas, focusing on how moral disapproval or indignation resembles anger and motivates punishment, while moral approval or praise resembles gratitude and motivates reward. These moral emotions differ from anger and gratitude in their apparent disinterestedness, impartiality, and generality, grounded in human social nature. They arise from sympathy, emotional contagion, aversion and disgust, and norm violations. In addition to Westermarck's moral psychology, the article examines his work on family formation and kinship as they relate to morality. It highlights connections to key theories of human cooperation, including kin selection, reciprocal altruism, indirect reciprocity, and gene-culture coevolution. The article concludes by exploring Westermarck's work on incest avoidance and the incest taboo in relation to his theory of moral emotions. It clarifies ambiguities in the literature on the incest taboo and illustrates how individual aversions can lead to sociocultural prohibitions across various domains. In addition to aversion-based rules, Westermarck also proposed a theory of sympathy-based rules, which is equally significant.