This book is the first comprehensive study of Westermarckian sociology and social anthropology, which flourished in Finland for half a century, until the Second World War. Edward Westermarck (1862–1939) was not only the founder of Finnish sociology but also Britain’s first professor of sociology, influencing and contributing to teaching and research at LSE for nearly three decades. In Finland, a group of disciples shared his Darwinian interest in the human mind and the comparative study of the origins of social phenomena. Like Westermarck, they also conducted extensive ethnographic fieldwork beyond Europe. Many of them became internationally renowned scholars who published their works through leading British publishers. The book traces his influence on British sociology and social anthropology more broadly also by considering his work and students at LSE, who emphasised their debt to Westermarck. Drawing on both published writings and unpublished archival material, the book offersa reinterpretation of ‘origin’ as the Westermarckian school’s core concept.