Monkey stone tools look like early human artifacts

A team of researchers led by the Max Planck Institute for Evolutionary Anthropology has recently analyzed fragments of a variety of stone tools used by long-tailed macaques (Macaca fascicularis) in the Phang Nga National Park in Thailand to crack open hard-shelled nuts. Since these monkeys frequently break their hammerstones and anvils, the assemblage of broken stones is quite significant and widespread in many parts of the landscape. 

To their surprise, the experts found that many of these artifacts have features that are similar to some of the earliest hominin stone artifacts currently known. Thus, in the absence of behavioral observations, the macaque tools would have likely been identified as anthropogenic in origin and interpreted as evidence of intentional tool production.

“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 artefacts and fossils. Our study shows that stone tool production is not unique to humans and our ancestors,” explained lead author Tomos Proffitt, a Paleolithic archeologist at Max Planck. 

“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 accidently produce a substantial archaeological record of their own that is partly indistinguishable from some hominin artifacts.”

By comparing these accidentally produced stone fragments to those produced by early hominins, the experts showed that many of the artefacts produced by macaques are virtually indistinguishable from the human-made ones. These findings shed new light on how one of the first known technologies may have emerged, suggesting that its origins could in fact be significantly older than previously thought and related to similar nut cracking behaviors.

“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,” said senior author Lydia Luncz, the head of the Technological Primates Research Group at Max Planck.

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

The study is published in the journal Science Advances.

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By Andrei Ionescu, Earth.com Staff Writer

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