Some monkeys unintentionally produce sharp-edged flakes
Stone tools may be by-products of using percussion tools
An international team of researchers has uncovered a new stone tool assemblage produced by yellow-breasted capuchins (Sapajus xanthosternos) in Fazenda Matos, Brazil, providing a fascinating possible window into the origins of stone tool technology in human evolution. Their findings reveal that primates, through everyday nut cracking behaviors, unintentionally produce sharp-edged flakes – a hallmark of early human stone tool assemblages.
The study builds on the team's previous work demonstrating that primates such as bearded capuchins and long-tailed macaques unintentionally create sharp flakes through stone percussion. By analyzing the diverse lithic material left behind by yellow-breasted capuchins, the researchers discovered similarities in flake and tool production to the archaeological signatures associated with early hominins.
“This is the first detailed analysis of a wild yellow-breasted capuchin stone tool assemblage,” said first author Tomos Proffitt of the Max Planck Institute for Evolutionary Anthropology and the Universidade do Algarve in Faro, Portugal. “Our findings build on previous work in stone tool using primate species that show that unintentional flake production should now be considered as a universal byproduct of percussive tool use across stone-tool-using primates.”
The research demonstrates that these sharp flakes – commonly linked with intentional tool production in the archaeological record – can emerge unintentionally during habitual nut-cracking activities. Moreover, the findings suggest that similar behaviors in early hominins more than 3 million years ago may have led to the development of intentional flake production and the eventual rise of advanced stone tool technologies like the Oldowan and Acheulean.
Sharp flakes may be byproducts of percussive behaviors
By comparing the Fazenda Matos assemblage with similar records from other primates, such as long-tailed macaques in Thailand, the team highlighted key differences, in the material signatures associated with this tool use, which are based on raw material availability such as the size of the flakes. However, universal across stone-tool using species is the production of sharp edged flakes.
“These results challenge the assumption that all sharp-edged flakes in the archaeological record represent deliberate tool production,” Lydia Luncz, the senior author of the paper and research group leader at the Max Planck Institute for Evolutionary Anthropology, added. “Instead, they suggest that some early stone tools may have been the byproducts of percussive behaviors rather than evidence of intentional actions.”
The study’s findings emphasize the importance of studying modern primates to explore the evolutionary roots of human behavior. “Our research underscores the need to broaden our perspective,” Proffitt said. “By incorporating the full spectrum of primate and hominin material records, we can better understand the pathways that led to the emergence of stone technology.”
