Joseph Henrich's The Weirdest People in the World asks why Western societies developed such unusual psychological traits and how those traits shaped global history. Henrich, a Harvard anthropologist, argues that people from Western, Educated, Industrialized, Rich, Democratic (WEIRD) societies are psychological outliers: more individualistic, guilt-oriented, analytically minded, and inclined to impartial moral reasoning than most humans throughout history. He traces these traits to an unexpected source: the medieval Catholic Church's marriage policies, which banned cousin marriage and thereby dissolved the extended kinship networks that characterized most human societies. Over centuries, this created nuclear family structures, voluntary associations, and eventually the psychological traits associated with modernity. Henrich marshals evidence from psychology, economics, history, and anthropology to build his argument, examining everything from visual perception tests to corruption indices to historical data on cousin marriage. The book is ambitious in scope, proposing a new framework for understanding the origins of Western individualism and its global consequences. Henrich is careful to distinguish description from prescription, noting that WEIRD psychology is not superior, merely different and historically unusual. The implications for understanding cultural diversity and development are profound. This is essential reading for anyone interested in the deep origins of modernity and the psychological diversity of humanity.