Rock-smashing monkeys make flakes like early stone tools

NEW YORK -- Call them knockoffs. Rock-smashing monkeys in Brazil make stone flakes that look a lot like tools made by our ancient ancestors.

Scientists watched as Capuchin monkeys in a national park pounded stones against each other, splitting off sharp-edged flakes that resemble cutting tools used by the forerunners of humans.

The monkeys ignored the flakes, focusing on the damaged stones instead. So they clearly weren't making them as tools. But if ancient monkeys did the same thing, their unintentional handiwork could be mistaken for tool-making by human ancestors, researchers said.

The scientists are not suggesting any stone tools attributed so far to human forerunners instead were made by monkeys, said Tomos Proffitt of Oxford University in England.

Those tools, which date back as far as 3.3 million years ago, are more complex than what the Brazilian monkeys make, he said in a telephone interview.

This image made available by the journal Nature shows examples of flaked stones made by wild capuchin monkeys in Brazil. (Tomos Proffitt, Angeliki Theodoropoulou via AP)

But as scientists look for earlier and earlier tools, their findings may begin to resemble the monkey flakes more strongly, said Proffitt, lead author of a study released Wednesday by the journal Nature. The work shows such flakes are not exclusively the calling card of our ancient ancestors, called hominins, he said.

Our African ancestors used sharp-edged stone flakes for butchering and skinning animal carcasses, as well as cutting up tough plant material. To show such flakes were human-made tools, scientists seek evidence such as wear marks on the edges or nearby animal bones with marks from butchering.

Proffitt and his co-authors studied capuchin monkeys in the Serra da Capivara National Park. They examined the flakes and damaged rocks and compared them to artifacts from human ancestors. It's not clear why the monkeys smash rocks together, he said.