A troop of monkeys in Brazil has smashed a long-held belief that only humans were smart enough to manufacture tools.
The capuchin monkeys were videoed happily banging one stone against another, chipping off sharp-edged rock flakes in the process.
These flakes look identical to the stone flake tools made by early humans.
But while our ancestors used the sharp edges for cutting and scraping objects, the monkeys preferred to lick off the stone dust and then throw the flakes away.
Prof Tomos Proffitt of Oxford University and colleagues travelled to South America to video the capuchins as they bashed stones together.
The monkeys very deliberately smashed the stones to break them apart but the resultant sharp flakes were an unintentional result of their efforts, the scientists write on Wednesday in the journal Nature.
The discovery is hugely important, however. The team collected stone fragments immediately after they were produced and these are virtually indistinguishable from the flakes produced intentionally by early humans.
This means there could be doubts about whether the stone tools found at early stone age sites were produced by humans or monkeys.
Hallmark
Scientists use the distinctive characteristics of flaked stone tools to distinguish them from naturally broken stones. The flakes have always been considered a hallmark of human involvement in the earliest stone tool technology, the authors write.
The capuchin’s party piece, a trick perhaps also repeated by its ancestors, undermines the assumption that the making of sharp flakes must have been achieved through human involvement.
The monkeys use two hands to pound a hammer stone against another, the goal being to break the stones open, the authors say. The animals then lick up the dust, perhaps to get at minerals inside or to consume lichens released by all the banging.
They discard the stone flakes once the dust has been licked off and they were never seen using the sharp edges to cut or scrape, the scientists add.
The research shows, however, that the production of sharp-edged stones can no longer be considered unique to humans.
