Harold Dibble demonstrated the systematic effects of reduction by retouch upon the size and shape of Middle Paleolithic tools. The result was the reduction thesis, with its far-reaching implications for the understanding of Middle Paleolithic assemblage variation that even now are incompletely assimilated. But Dibble’s influence extended beyond the European Paleolithic. Others identified additional reduction methods and measures that complement Dibble’s reduction thesis, and applied analytical concepts and methods consistent with it to industries and assemblages around the world. These developments facilitated comprehensive reduction analysis of archaeological tools and assemblages and their comparison in the abstract despite the great diversity of their time–space contexts. Dibble argued that many assemblages are time-averaged accumulations. In cases from New Zealand to North America, methods he pioneered and that others extended reveal the complex processes by which behavior, tool use, curation, and time interacted to yield those accumulations. We are coming to understand that the record is no mere collection of ethnographic vignettes, instead a body of data that requires macroarchaeological approaches. Archaeology’s pending conceptual revolution in part is a legacy of Dibble’s thought.