LONDON: The path of human evolution may need to be rewritten after archaeologists discovered that monkeys also produce "tool-like flakes" which were thought to be uniquely man-made.
A band of wild bearded capuchin monkeys in Brazil were spotted hammering rocks to extract minerals, causing large flakes too fly off which resemble those which were considered to be distinctively human.
Previously archaeologists believed the flakes could only be made through a process called "stone-knapping" where a larger rock is selected and hammered with another stone to produce sharp blade-like slithers for use as arrows, spears or knives.
The flakes were thought to represent a turning point in human evolution because they demonstrated planning, cognition and hand manipulation that cannot be achieved by other animals.
But the new research suggests that flakes can be made without any such foresight. In fact they can simply be made by accident.
"The fact that we have discovered monkeys can produce the same result does throw a bit of a spanner in the works in our thinking on evolutionary behaviour and how we attribute such artefacts," said Dr Michael Haslam, of the Primate Archaeology project at the University of Oxford. "Our understanding of the technologies adopted by our early ancestors helps shape our view of human evolution. The emergence of sharp-edged stone tools that were ... hammered to create a cutting tool was a big part of that story."
A team from Oxford, University College and the University of Sao Paulo studied monkeys in the Serra da Capivara National Park in Brazil. The capuchins were observed engaging in "stone on stone percussion", whereby they selected rounded quartzite cobbles and then struck the "hammer-stone" forcefully and repeatedly on quartzite cobbles embedded in a cliff.
Their actions dislodged more cobbled stones and also fractured their hammer-stones, so that flakes flew off.
The team identified complete and broken hammer-stones and complete and fragmented flakes, half of which had "conchoical" fractures where the break is round and smooth in appearance like a shell. It was previously thought that such fractures could only made by hominids.
The researchers believe that the capuchins hammer the stones to extract powdered silicon, an essential trace nutrient, or to remove lichen for some unknown medicinal purpose. None of the monkeys tried to cut or scrape using the flakes.
Lead author Dr Tomos Proffitt, from the School of Archaeology at Oxford, said: "Within the last decade, studies have shown that the use and intentional production of sharp-edged flakes are not necessarily linked to early humans who are our direct relatives, but instead were used and produced by a wider range of hominins."
The research was published in the journal Nature.