Chromosome surveys of human populations: between epidemiology and anthropology. 
It is commonly held that after 1945 human genetics turned medical and focussed on the individual rather than on the study of human populations that had become discredited.  However, a closer look at the research practices at the time quickly reveals that human population studies, using old and new tools, prospered in this period.  The essay focuses on the rise of chromosome analysis as a new tool for the study of human populations.  It reviews a broad array of population studies ranging from newborn screening programmes to studies of isolated or 'primitive' people.  Throughout, it highlights the continuing role of concerns and opportunities raised by the propagation of atomic energy for civilian and military uses, the collection of large data bases and computers, and the role of international organisations like the World Health Organisation and the International Biological Programme in shaping research agendas and carving out a space for human heredity in the postwar era.