The world's oldest tools - made by ancestors of modern humans around 3.3 million years ago - have been found in Kenya.
Stones had been deliberately "knapped" or flaked to make a sharp cutting edge, researchers said, according to Science magazine.
They are about 700,000 years older than the previous record holder and are likely to have been made by Australopithecus, an ape-like ancestor of Homo sapiens, or another species, Kenyanthropus.
Archaeologist Sonia Harmand, of New York's Stony Brook University, told the annual meeting of the United States Paleoanthropology Society: "The artefacts were clearly knapped and not the result of accidental fracture of rocks." About 150 flakes, the stones they were taken from and anvils on which the stones were placed while they were struck were found near Lake Turkana in Kenya.
In 2010, researchers in Dikika in Ethiopia said they had found cut marks on animal bones that were 3.4 million years old, but their claim that this showed the use of tools was disputed.
