Skulls and Statistics: Karl Pearson and Competing Methods of Classifying Races in the Early 20th Century

Historians often assume that physical anthropology before 1945 relied on a simple typological, descriptive method to analyze skulls and classify races, which was only successfully challenged by populational genetics after World War II. This paper revisits and complicates this history by turning our attention to a fundamental attack on the typological tradition before 1945: by Karl Pearson, his introduction and development of statistical methods in anthropology, and the racial research his Biometric Laboratory produced between 1900-1938. The application of complex statistical formulae to the study of skulls and race unsettled long standing anthropological methods and theories. Whereas anthropologists had long studied the skull by itself, identifying racially-representative “types,” biometricians turned crania into means, standard deviations, and probable errors fit for statistical analysis. “Pearsonian anthropology” greatly expanded a geometric approach to craniometry which was already present in older anthropological practices. This paper argues that Pearson’s approach to craniometry set the stage for a durable relationship between biometry, geometry, and the skull that continues to live on in present-day biometric practices and technologies. At the same time, the paper discusses how anthropologists questioned Pearson’s approach and only partially adopted statistical methods, suggesting that the relationship between skulls and statistics was not sturdy but shaky and not fully trusted. The history of Pearson’s interventions in physical anthropology thus reveals deep divisions concerning the methods of classifying races well before 1945.