White-faced capuchins (Cebus capucinus imitator) exhibit selectivity for stone tools

Abstract

Over the last few decades, the developing field of primate archaeology has used archaeological methods to reconstruct primate behaviors, especially tool use. We expand the possibilities of primate archaeology with an inverse approach: using living primates to address archaeological questions. In particular, we investigate tool selectivity, a phenomenon that not only represents a significant milestone for tool users, also for the emergence of stone tool technology in human evolution. Observing extant primate tool use can establish clear expectations for a percussion-based archaeological record across taxa. Here, we describe stone tools assemblages produced by two independent populations of white-faced capuchin monkeys (Cebus capucinus imitator) in Coiba National Park, Panama, and provide evidence of stone tool selectivity in both populations. We demonstrate that capuchins select for tool dimensions, and select different sizes for different tool functions. This selectivity analysis reveals that primate stone tool use results in assemblages of artifacts that are distinct from natural accumulations of unused material in the surrounding landscapes. These variations further suggest that stone tool use has a recognizable signature at the assemblage level, even where no lithic flaking occurs. The existence of such assemblage-level signatures offer new avenues for the archaeological identification of tool use both in unhabituated living primates and extinct taxa. The presence of selectivity in multiple capuchin populations suggests that, along with percussion, tool selectivity is ancestral to stone tool flaking, and is shared by phylogenetically distant branches of the primate tree.