Flake production: A universal by-product of primate stone percussion

The evolution of stone tool technology marks a significant milestone in hominin development, enabling early humans to manipulate their environments. The oldest known evidence, dating to 3.3 Ma, indicates a combination of percussive and flake production activities. Studying the archaeological signature of percussive stone tool use in living primate provides a potential analog to the origin of stone flake technology in the hominin lineage. Here, we present a yellow-breasted capuchin (Sapajus xanthosternos) stone tool assemblage from Fazenda Matos, Brazil, to explore the variability of the material signatures associated with percussive tool use. Our analysis of this record demonstrates many archaeological features previously associated with intentional flake production. This includes hammerstones with substantial percussive damage and a range of flaked and detached pieces. Comparative analyses with other flaked primate and hominin assemblages reveals that, unintentional flake production is a universal component of stone hammer and anvil percussive behaviors, suggesting that similar behaviors by early hominins may have led to stone flake technology and that this record may have been highly variable. To fully understand the origins of hominin stone technology, a broad spectrum of material records including both hominin and primate must be considered.