Deliberately produced sharp stone flakes and chipped pieces are our main evidence for the rise of technology in our lineage. This evidence is being used to decipher the earliest hominin behaviour, cognition and subsistence strategies.

In a new study, scientists at the Max Planck Institute for Evolutionary Anthropology have discovered artifacts made by ancient world monkeys in Thailand that resemble stone tools. These artifacts resemble stone tools, historically found to have been intentionally created by early hominins.

The study has challenged long-held beliefs about the origins of intentional tool making in our lineage.

The study is based on recent research of stone tools made by long-tailed macaques in Thailand’s Phang Nga National Park. These monkeys crack open nuts using stone tools. The monkeys regularly smash their anvils and hammerstones. The resulting collection of broken stones is extensive and scattered across the countryside. In addition, many of these artifacts share the same characteristics that can be used to distinguish intentionally made stone tools from other types of stone tools in some of the earliest archaeological sites in East Africa.

flakes with sharp edges
Examples of sharp-edged flakes inadvertently produced by long-tailed macaques. © Proffitt et al, 2023

Lead author Tomos Proffitt, a researcher at the Max Planck Institute for Evolutionary Anthropology, said: “The ability to deliberately create sharp stone chips is seen as a pivotal point in hominin evolution, and understanding how and when this happened is a major question typically explored through the study of artifacts and fossils from the past. Our study shows that stone tool production is not unique to humans and our ancestors.”

“That these macaques use stone tools to process nuts is not surprising, as they also use tools to access various shellfish. Interestingly, in doing so, they accidentally produce a substantial archaeological record that is partially indistinguishable from some hominid artifacts.

The scientists showed that many of the ape-generated artifacts fall within the range of those commonly associated with early hominins by comparing the inadvertently created stone fragments formed by the macaques to those found at some of the earliest archaeological sites.

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

The recently discovered macaque stone tools offer new insights into how our earliest ancestors developed the first technology. They suggest that this origin may be related to behavior similar to nut cracking that may be much older than the earliest archaeological records.

Lydia Luncz, senior author of the study and head of the Technological Primates Research Group at the Max Planck Institute for Evolutionary Anthropology, said: “The cracking of nuts using stone hammers and anvils, similar to what some primates do today, has been suggested by some as a possible precursor to the deliberate production of stone tools. This study, together with previous studies published by our group, opens the door to identifying such an archaeological signature in the future.”

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

Magazine reference:

  1. Tomos Proffitt, Jonathan S. Reeves et al. Wild macaques challenge the origins of intentional tool manufacturing. Scientific progress. Paper link.