By chance, some monkeys create stone flakes that look like those used by early humans.

• Rating

• boulders
• macaque
• monkey
• creations
• anthropology
• discovered

The discovery indicates that not all Stone Age cutting tools were deliberate creations but rather the result of happenstance.

Southern Thai monkeys smash off chunks of stone from their improvised nutcrackers as they use boulders to split open oil palm nuts. Researchers believe that ancient humans intentionally fashioned these flakes to mimic other sharp-edged stone tools.

Fragments made by the long-tailed macaques (Macaca fascicularis) of Thailand have been compared to those discovered at 17 East African hominid sites dating back between 3.3 and 1.56 million years ago. Researchers publish their discovery in the March 10 issue of Science Advances, which implies that ancient humans may have accidentally formed the stone flakes while using rocks to break nuts, bones, and other materials.

Earlier studies have demonstrated that capuchin monkeys in Brazil unknowingly create stone flakes with human characteristics when they smash them with their bare hands (SN: 10/19/16).

Proffitt claims (SN: 6/3/19) that observations of rock smashing by these two monkey species disprove the long-held theory that ancient stone flakes, including some of the oldest known instances of tools, must have been purposely produced by humans. He thinks the methods used to make such judgements should be reexamined.

In 40 locations on the island where macaques reside, Proffitt and his team found 219 stone flakes, both whole and broken. The crew also came across rocks that showed signs of having been pounded, possibly with a tool or as a platform.

Proffitt, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, claims that there are distinguishing characteristics between macaque and hominin stone flakes. For instance, whereas hominid artefacts often show damage on both sides, macaque flakes typically only show damage on one side.

CITATIONS

T. Proffitt et al. Wild macaques challenge the origin of intentional tool production. Science Advances. Published March 10, 2023. doi: 10.1126/sciadv.ade8159.