Scientists Discover Surprising Similarities in Stone Tools of Early Humans and Monkeys

Long Tailed Macaque

Example of a long-tailed macaque using a stone tool to access food. Credit: Lydia V. Luncz

Macaques unintentionally created stone fragments that bear a resemblance to some of the earliest stone artifacts crafted by early hominins.

The study focuses on fresh analyses of stone tools employed by long-tailed macaques in Thailand’s Phang Nga National Park. These primates utilize stone tools to open tough-shelled nuts, frequently causing their hammerstones and anvils to break in the process.

The collection of fragmented stones that results from this process is both significant in size and extensively distributed across the terrain. Furthermore, numerous artifacts exhibit the same traits typically associated with purposefully crafted stone tools found at some of the earliest archaeological sites in East Africa.

“The ability to intentionally make sharp stone flakes is seen as a crucial point in the evolution of hominins, and understanding how and when this occurred is a huge question that is typically investigated through the study of past artifacts and fossils. Our study shows that stone tool production is not unique to humans and our ancestors,” says lead author Tomos Proffitt, a researcher at the Max Planck Institute for Evolutionary Anthropology.

“The fact that these macaques use stone tools to process nuts is not surprising, as they also use tools to gain access to various shellfish as well. What is interesting is that, in doing so they accidentally produce a substantial archaeological record of their own that is partly indistinguishable from some hominin artifacts.”

Sharp Edged Stone Flakes

Examples of sharp-edged flakes produced unintentionally by long-tailed macaques. Credit: Proffitt et al, 2023

New insights into the evolution of stone tool technology

By comparing the accidentally produced stone fragments made by the macaques with those from some of the earliest archaeological sites, the researchers were able to show that many of the artifacts produced by monkeys fall within the range of those commonly associated with early hominins.

Co-lead author Jonathan Reeves highlights: “The fact that these artifacts can be produced through nut cracking has implications for the range of behaviors we associate with sharp-edged flakes in the archaeological record..”

The newly discovered macaque stone tools offer new insights into how the first technology might have started in our earliest ancestors and that its origin may have been linked to similar nut cracking behavior which could be substantially older than the current earliest archaeological record.

“Cracking nuts using stone hammers and anvils, similar to what some primates do today, has been suggested by some as a possible precursor to intentional stone tool production. This study, along with previous ones published by our group, opens the door to being able to identify such an archaeological signature in the future,” says Lydia Luncz, senior author of the study and head of the Technological Primates Research Group at the Max Planck Institute for Evolutionary Anthropology.

“This discovery shows how living primates can help researchers investigate the origin and evolution of tool use in our own lineage”

Reference: “Wild macaques challenge the origin of intentional tool production” by Tomos Proffitt, Jonathan S. Reeves, David R. Braun, Suchinda Malaivijitnond and Lydia V. Luncz, 10 March 2023, Science Advances.
DOI: 10.1126/sciadv.ade8159

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