Wild Monkeys Make Stones That Resemble Human Tools

Wild bearded capuchin monkeys in Brazil have been observed making what appears to be human-like tools. According to reporting in The Christian Science Monitor, they are sharp edged stone flakes, similar to primitive stone tools that early humans used.

“Its an incredibly interesting behavior,” says study leader author Tomos Proffitt, an archeologist at the University of Oxford. “Another species is making sharp, conchoidally fractured flakes, an artifact that we only ever thought is unique to hominids.”

During research they have found that the monkeys are using ‘hammer stones,’ and using them to hit quartz cobbles stuck in a large rock conglomerate wall. As the monkeys hit the quartz repeatedly, flakes broke off the hammer stone.

“In terms of a technique of making flakes, this is a very similar technique to what has been hypothesized was the technique to make the very first archaeological flakes,” Dr. Proffitt said to CSM. In that technique, called passing hammer knapping, the tool maker hits a stationary stone with a hammer stone, breaking flakes off the hammer stone and keeping the hammer stone intact.

Despite the similarities, Proffitt says this doesn’t really change the human archaeological record, as the most ancient of these stones flakes were found in places that had other telltale signs of human (rather than primate) activity.

When knappers intentionally create stone flakes, they work on the stone to create as many flakes and as much dust as possible. Dr. Stout, a professor at paleolithic archeology at Emroy University, tries to explain. So with the 2.6 million year old artifacts associated with early humans, he says, archeologists find many more flakes to each core than the capuchins create.

“They’re producing objects that are visually similar to the most distinctive component of human stone tool technology,” Dr. Shea, another archeologist at the University of Oxford, tells the monitor. “[But] humans use the flakes to cut things, capuchins don’t.”

The monkeys seem to pay the flakes no mind, instead researchers see them focusing on the quartz dust produced by smashing the rocks, which the monkeys lick. Perhaps to ingest the mineral in the rocks.

Until researchers can figure out why the primates are banging rocks together, the impact of this study is simply that, “this behavior that we don’t understand can produce things that look like this other behavior, making tools for cutting meat and that sort of thing.” Dr. Shea says.

Capuchins, like most primates, are omnivores that may eat other creatures (like small mammals and insects), but have never been observed using stones to “butcher” them the way a human would.