The document discusses the relationship between socioeconomic status and health. It notes that scholars in the mid-19th century like Engels, Wirchow, and Allende observed that social structures of oppression and features of urban life contributed to the spread of infectious diseases. While the biomedical model dominated understandings of disease in the early 20th century, awareness of the social determinants of health reemerged in the 1960s. The introduction provides historical context on perspectives of the social origins of illness and the socioeconomic inequalities in health outcomes.