It did not gain a significant foothold in the United States, because American society was thought to be socially mobile, classless, and oriented to the individual. This neglect of Marxism by American sociologists, however, was not due to scholarly ignorance. Sociologists of all periods had read Marx as well as Charles A. Beard’s economic interpretation of American history and the work of Werner Sombart (who had been a Marxist in his early career). Instead, in the 1960s, neo-Marxism—an amalgam of theories of stratification by Marx and Max Weber—gained strong support among a minority of sociologists. Their enthusiasm lasted about 30 years, ebbing with the breakup of the Soviet system and the introduction of postindustrial doctrines that linked class systems to a bygone industrial era. The persistence of social and economic inequality is now explained as a complex outcome of factors, including gender, race, and region, as well as global trade and national politics.

Human ecology

Representing the second theoretical area, human geographers—Ellsworth Huntington, Ellen Semple, Friedrich Ratzel, Paul Vidal de La Blache, Jean Brunhes, and others—emphasized the impact of climate and geography on the evolution of those societies that flourished in temperate zones. Their theories found no place in mainstream sociological thought, however, except for a brief period in the 1930s when human ecology sought to explain social change by linking environmental conditions with demographic, organizational, and technological factors. Human ecology remains a small but vital part of sociology today.

Psychological theories emphasized instincts, drives, motives, temperament, intelligence, and human sociability in social behaviour and societal evolution. Social psychology modifies these concepts to explain the broader phenomena of social interaction or small group behaviour. Although American sociology even today retains an individualistic (and therefore psychological) bias, by the 1930s sociologists had concluded that psychological factors alone could not explain the behaviour of larger groups and societies.

Finally, cultural theories of the 1930s emphasized human ability to innovate, accumulate, and diffuse culture. Heavily influenced by social and cultural anthropology, many sociologists concluded that culture was the most important factor in accounting for its own evolution and that of society. By 1940 cultural and social explanations of societal growth and change were accepted, with economic, geographic, and biopsychological factors playing subsidiary roles.