The study of lives and the life course represents an enduring interest of the social sciences and reflects important social changes over the twentieth century. Most notably, developments after World War II called for new ways of thinking about people's lives, about society, and about their connection. Pioneering longitudinal studies of American children, launched in the 1920s and 1930s (Eichorn, Clausen, Haan, Honzik, & Mussen, 1981), became studies of the young adult in postwar America, thereby focusing attention on social trajectories that extend across specific life stages. In addition, the rapidly changing demography of society assigned greater significance to the problems of aging and to their study. Insights regarding old age directed inquiry into earlier phases of life and into the process by which life patterns are shaped by a changing society.

This chapter presents the life course as a theoretical orientation for the study of human development that incorporates temporal, contextual, and processual distinctions. In concept, the life course refers to age-graded life patterns embedded in social structures and cultures that are subject to historical change. These structures vary from social ties with family and friends at the micro level to age-graded hierarchies in work organizations and to the policy dictates of the state. Change in the life course shapes the content, form, and process of individual development, and such change may be prompted in part by the maturation or aging of the individual as well as by social forces.