The archaeological visibility of chimpanzee (Pan troglodytes) nut-cracking

The earliest evidence for complex tool-use in the archaeological record dates back to 3.3 Ma. While wooden tools may have been used by our earliest ancestors, its evidence is absent due to poor preservation. However, insights into possible early hominin wooden tool-use can be gained from observing the tool-use practices of our closest living relatives, chimpanzees. By using stone hammers to crack various nuts, chimpanzees leave a durable material signature comprised of formal tools and associated diagnostic fragments. While the archaeological evidence of chimpanzee wooden tool-use is temporary, the combination of stone hammers and wooden anvils can create a more enduring lithic record. This study explores the lithic assemblages associated with wooden and stone anvil use at nut cracking sites in Taï National Park, Côte d’Ivoire, using technological and use-wear analyses. Our results indicate clear differences in density, fracture patterns, and use-wear in the lithic records between wooden and stone anvil sites. New archaeological excavations at six chimpanzee nut cracking sites reveal that the anvils' material directly influences the visibility of nut cracking evidence in the archaeological record. By examining the nature of the lithic signatures associated with wooden and stone anvil use, we can formulate hypotheses about the probability of such behaviors being preserved and identifiable in the Plio-Pleistocene hominin archaeological record.