Scientists at the Max Planck Institute for Evolutionary Anthropology have found artifacts built by Old World monkeys in Thailand that resemble stone tools historically thought to have been deliberately made by early hominins.
Sharp-edged stone tools were previously thought to mark the beginning of the purposeful manufacture of stone tools, one of the defining and characteristic features of hominid evolution. This new study challenges long-held assumptions about the origins of purpose-built tools in our own line.
The research is based on new analyzes of stone tools used by long-tailed macaques in Phang Nga National Park, Thailand. These monkeys use stone tools to crack hard-shelled nuts. Monkeys often break their hammers and anvils in the process. The resulting assemblage of broken stones is considerable and spread over the landscape. Additionally, many of these artifacts bear all the same characteristics commonly used to identify purpose-made stone tools at some of the oldest archaeological sites in East Africa.
“The ability to deliberately create sharp stone flakes is considered a key point in hominin evolution, and understanding how and when this happened is a huge question that is usually explored by studying past artifacts and fossils. Our study shows that stone tool making is not unique to humans and our ancestors,” said lead author Tomos Proffitt, a researcher at the Max Planck Institute for Evolutionary Anthropology.
He also says “The fact that these macaques use stone tools to process nuts is not surprising , as they also use tools to gain access to various molluscs. Interestingly, in doing so, they accidentally produce their own significant archaeological record that is partially indistinguishable from some hominins.”
New insights into the development of stone tool technology
By comparing randomly produced stone fragments produced by the macaques with those from some of the oldest archaeological sites, the researchers were able to show that many of the artifacts produced by the apes fall within the range of those commonly associated with early hominins.
Co-author Jonathan Reeves said: “The fact that these artefacts can be made by cracking nuts has implications for a range of behaviors that we associate with sharp-edged flakes in the archaeological record.”
Newly discovered macaque stone tools offer new insight into how the first technology might have started in our earliest ancestors, and that its origins might be related to a similar nut-cracking behavior that could be significantly older than the current oldest archaeological record.
“Cracking nuts with stone hammers and anvils, similar to what some primates do today, has been suggested by some as a possible precursor to the deliberate manufacture of stone tools. This study, along with previous studies published by our group, opens the door to identifying such an archaeological signature in the future,” said Lydia Luncz, lead author of the study and head of the Technology Primates Research Group at Max Planck. Institute for Evolutionary Anthropology and adds: “This discovery shows how living primates can help researchers investigate the origins and evolution of tool use in our own lineage.”
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