Theoretical advances of some note often evolve from modest beginnings and unplanned circumstances. This observation applies to ways of thinking about the social pathways of people’s lives and their historical times. Perspectives of this kind owe much to a band of American psychologists in the 1920s who launched a series of longitudinal studies of child development (see Elder, 1998). They broke new ground with support from colleagues in other disciplines. Sociologist W. I. Thomas claimed in the mid-1920s that priority should be given to the “longitudinal approach to life history” and that studies should investigate “many types of individuals with regard to their experiences and various past periods of life in different situations” (in Volkart, 1951, p. 593). Thomas had in mind a study that followed children from their earliest years to young adulthood. The first half of life, he assumed, would set in motion the pathways of later life.