The world's oldest butchering tools dating back 2.5 million years helped our ancestors to communicate, experts have said.
Hominin ancestors in the African savannah used shaped rocks and shards to cut apart animals that had been hunted for their meat – a technology that spread throughout the continent and came to be a massive force in the evolution of human communication.
Scientists at the University of California, Berkeley, the University of Liverpool and the University of St. Andrews looked at archaeology, psychology and evolutionary biology to find out how early Stone Age tools aided our development.
Their study, published in the journal Nature Communications, examined Oldowan tools – the oldest known cutting devices ever used by early man.
Lead author Thomas Morgan said: "Our findings suggest that stone tools weren't just a product of human evolution, but actually drove it as well, creating the evolutionary advantage necessary for the development of modern human communication and teaching."
Findings suggest that teaching and a primitive form of language started to emerge 1.8 million years ago.
Oldowan stone-knapping involves hammering a hard rock against softer ones like basalt or flint to create butchering flakes. This technique is first found in eastern Africa in the Lower Palaeolithic period and did not change for about 700,000 years, when hand axes and cleavers were developed.
Scientists compared spoken communication versus imitation to see which technique led to the best quality and highest volume of flakes, with least waste. Verbal cues were found to be most effective.
However, the scientists say this does not mean Oldowan hominins spoke to one another. "These tools are the only tools they made for 700,000 years. So if people had language, they would have learned faster and developed newer technologies more rapidly."
Instead, the study suggests that the "seeds of language" were planted as a result of tool demand and that at some point, their language skills improved, resulting in Acheulean hand-axes and cleavers.
"To sustain Acheulean technology, there must have been some kind of teaching, and maybe even a kind of language, going on, even just a simple proto-language using sounds or gestures for 'yes' or 'no,' or 'here' or 'there,'" Morgan said.
"At some point they reached a threshold level of communication that allowed Acheulean hand axes to start being taught and spread around successfully and that almost certainly involved some sort of teaching and prototype language."