RESUMEN
This article analyzes how evolving pharmaceutical technology, chemical advances, and world politics created the need for an abundant and cheap supply of steroids, and how decisions made in faraway laboratories ultimately determined that a Mexican yam, barbasco, was the best possible raw material. Following this discovery, this article explores how barbasco's exploitation impacted on the Mexican countryside and specifically the men and women hired to gather wild yams. In analyzing, for example, the peasant organizations that emerged, the use of chemical terms by barely literate peasants, and the Mexican government's political strategy to control rural unrest by controlling barbasco production one begins to understand the unexpected consequences of the global search for medicinal plants. In this particular case, the merging of science and peasant life reshuffled social hierarchies in the countryside, granted monetary value to an erstwhile 'weed', and gave a novel reinterpretation to laboratory knowledge and its (social) uses.