Researchers have found that the primitive humans who lived 2.75 million years ago at an archaeological site called Namorotukunan used stone tools continuously for 300,000 years. Evidence previously suggested that early human tool use was sporadic: randomly developed and quickly forgotten. The Namorotukunan find is the first to show that the technology was passed down through thousands of generations.

According to Prof David Braun, of George Washington University, in Washington DC, who led the research, this find, published in the journal Nature Communications, provides incredibly strong evidence for a radical shake-up in our understanding of human evolution. "We thought that tool use could have been a flash in the pan and then disappeared. When we see 300,000 years of the same thing, that's just not possible," he said. "This is a long continuity of behaviour. That tool use in (humans and human ancestors) is probably much earlier and more continuous than we thought it was."

Archaeologists spent ten years at Namorotukunan uncovering 1,300 sharp flakes, hammerstones, and stone cores, each made by carefully striking rocks gathered from riverbeds. These are made using a technology known as Oldowan and is the first widespread stone tool-making method. The same kinds of tools appear in three distinct layers. The deeper the layer the further back the snapshot in time. Many of the stones were specially chosen for their quality, suggesting that the makers were skilled and knew exactly what they were looking for, according to the senior geoscientist on the research team, Dr Dan Palcu Rolier of the University of São Paulo in Brazil. "What we see here in the site is an incredible level of sophistication," he told BBC News.

"These guys were extremely astute geologists. They knew how to find the best raw materials and these stone tools are exceptional. Basically, we can cut our fingers with some of them." Geological evidence suggests that tool use probably helped these people survive dramatic changes in climate. The landscape shifted from lush wetlands to dry, fire-swept grasslands and semideserts," said Rahab N. Kinyanjui, senior scientist at the National Museums of Kenya. (BBC/David Braun)