Lydia V. Luncz illustrates a long-tailed macaque who uses a stone tool to access food.
Long-tailed macaques in Thailand's Phang Nga National Park are studying new techniques for breaking their hammerstones and anvils in the process.
The fragmented stones that result from this process are both large and wide spread across the country. Furthermore, many artifacts bear the same characteristics as purposefully crafted stone tools found at some of East Africa's oldest archaeological sites.
According to lead author Tomos Proffitt, the ability to intentionally crush stone flakes is considered to be a critical event in the evolution of hominins. This is a huge topic that is typically investigated through the examination of previous artifacts and fossils.
“It’s not surprising that these macaques use stone tools to grind nuts, as they also use tools to gain access to various shellfish.”
Long-tailed macaques produce sharp-edged flakes accidentally, according to Proffitt et al., 2023.
The researchers were able to demonstrate that many of the monkey's' stone fragments were created accidentally, and that they corresponded to early hominins.
Jonathan Reeves, a co-lead author, says, "The fact that these artifacts may be obtained via nut cracking has implications for the variety of behaviors we associate with sharp-edged flakes in the archaeological record."
The newly discovered macaque stone tools provide new insight into how our earliest descendants might have used the first technology, and that its origin might be linked to a similar nut cracking behavior that is likely to be decades older than the current archaeological record.
Some have suggested that cracking nuts with stone hammers and anvils, as a possible precursor to intentional stone tool manufacturing. This work, along with previous ones published by our group, opens the way to exploiting such an archaeological signature in the future.
"This finding demonstrates how living primates can assist researchers in their investigation of tool use in our own lineage."
Tomos Proffitt, Jonathan S. Reeves, David R. Braun, Suchinda Malaivijitnond, and Lydia V. Luncz, a reference, have published a paper on "Wild macaques challenge the origins of intentional tool manufacturing." DOI: 10.126/sciadv.ade8159.