Researchers Observe Monkeys Making Stone Flakes, Materials Previously Only Attributed to Hominins

A team of researchers has discovered that capuchin monkeys sometimes make stone flakes when breaking open rocks. The primates don’t use the flakes as tools, as early humans did, but are instead trying to gain access to lichen and minerals hidden in the rocks. The findings may change the way archaeologists classify old stone flakes, which were previously believed to be crafted by early hominins exclusively. The details are in a paper that was just published in the journal Nature.

Archaeologists have long considered the presence of sharp-edged stone flakes as indicative of early hominin activity. The flakes were considered to be early tools and it was understood that only hominins crafted them.

In a collaboration between the University of Oxford, the University College London and the University of São Paulo, a team of researchers discovered that monkeys were inadvertently making the same stone flakes. Wild bearded capuchin monkeys (Sapajus libidinosus) in Brazil were seen cracking open rocks to get to minerals and nutritious lichen. In the process, they were creating stone flakes. The monkeys did not use them as tools, they were simply byproducts. They used quartzite rocks as hammers and the rocks began to chip with use.

The team’s observations may change how archaeological materials are classified since capuchins were seen making the same stone flakes attributed to early Homo species. The findings also provide new insights into the cognitive requirements of creating the “tools”. If monkeys are able to make the stone flakes through natural behaviors, it may not be as complex of a task as previously believed. This also changes our understanding of the evolution of tool use. Early tool-making may have arisen in humans through unintentional behaviors similar to the capuchins’ flake crafting. The authors note that most early archaeological records are probably accurate but that the presence of stone flakes is no longer a definite sign of hominin tool-making.


Proffitt et al. Wild monkeys flake stone tools. Nature (2016).

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