Bedrock mortars recur in the record of many prehispanic communities. However, few studies discuss their relationship with social processes. In the present work, we discuss a regional study of bedrock mortars in the semiarid north of Chile, specifically the Limarí River basin (30° S). Using a combination of formal, spatial, contextual, archaeobotanical, and absolute dating analyses, we assess the chronology of bedrock mortars and how they related to social processes of hunter-gatherer populations of the region (2000 BC to AD 1000). In particular, we suggest that an increase in production of bedrock mortars among pottery-using hunter-gatherer groups (AD 1–1000) can be observed, associated with a greater intensity of plant collection and use, and a diminution in the importance of hunting. This situation led to a set of new social relationships structured on the practice of collective grinding and shared use of bedrock mortars. These results show the importance of this material record as a means of approaching aspects of prehispanic social life, and demonstrates a methodological framework within which to interrogate this materiality by combining different analytical levels of bedrock mortars’ variability.