Researchers in Kenya have discovered stone tools 3.3 million years old — the oldest on record by 700,000 years — confirming long-held doubts about our ancestors’ reputation as first adopters of a pivotal technology.
Until the new discovery, described Wednesday in the journal Nature, the oldest stone tools dated roughly to the origins of the genus Homo, the lineage that gave rise to modern humans. The Kenyan cache — 149 large stones with clear, if crude, signs of purposeful flaking and chipping — coincides with the era of much more ancient hominins like Australopithecus.
“We knew at the moment of discovery that they would be the oldest stone tools in the world,” said Jason Lewis, a co-author on the paper and a paleoanthropologist at Stony Brook University’s Turkana Basin Institute. “Once the geological analyses came back later that year that in fact they were older than 3 million years, we were even more astonished.”
The discovery is “really exciting,” said Richard Potts, director of the Smithsonian Institution’s Human Origins Program, who was not involved in the research.
Yet until we know more about who used the stones and how, Potts says, crucial questions remain. Are these artifacts evidence of an isolated outburst of the type of handiness we share with chimpanzees, or of a slowly evolving — and eventually planet-altering — behaviour?
“Is it part of that general capacity? Or is it something that really is the beginning of that major milestone: the beginning of human technology?”
Until now, the oldest known stone tools were found in Ethiopia and belonged to the 2.6 million-year-old “Oldowan” culture. Those dates coincide with the emergence of Homo, the genus that gave rise not only to Homo sapiens but also extinct human cousins like Neanderthals.
Yet for some time, scientists have suspected that Oldowan artifacts are too sophisticated to be the first attempt at a technology that, crucially, unlocks the huge pool of calories trapped inside hard-shelled nuts and hide-bound animals. And since some chimpanzees use sticks to poke at insects and even, occasionally, rocks to bash nuts, some researchers believed tool-making behaviour emerged as far back as the common ancestor of chimpanzees and humans.
“I think the entire community was ready for someone to find older stone tools,” said Sonia Harmand, another co-author of the Nature paper. Yet when they did, Harmand says, they were much more unusual than anyone anticipated: unlike Oldowan tools, which were hand-held, these required an anvil.
So who made them: small-brained hominins like Australopithecus, or a Homo ancestor 500,000 years older than the most ancient ever discovered? Are the Kenyan tools an isolated occurrence, or evidence of the slow build of a transformative technology — if so, one that should be scattered elsewhere in the archaeological record? The findings have important implications for whether the evolutionary traits that eventually marked Homo sapiens began in a sudden, environment-driven adaptive burst, or arrived after a slow build.
“Terrific new questions. Much work to do,” Potts said.