SAN FRANCISCO, CALIFORNIA—Researchers at a meeting here say they have found the oldest tools made by human ancestors—stone flakes dated to 3.3 million years ago. That’s 700,000 years older than the oldest-known tools to date, suggesting that our ancestors were crafting tools several hundred thousand years before our genus Homo arrived on the scene. If correct, the new evidence could confirm disputed claims for very early tool use, and it suggests that ancient australopithecines like the famed “Lucy” may have fashioned stone tools, too.

Until now, the earliest known stone tools had been found at the site of Gona in Ethiopia and were dated to 2.6 million years ago. These belonged to a tool technology known as the Oldowan, so called because the first examples were found more than 80 years ago at Olduvai Gorge in Tanzania by famous paleoanthropologists Louis and Mary Leakey. Then, in 2010, researchers working at the site of Dikika in Ethiopia—where an australopithecine child was also discovered—reported cut marks on animal bones dated to 3.4 million years ago; they argued that tool-using human ancestors made the linear marks. The claim was immediately controversial, however, and some argued that what seemed to be cut marks might have been the result of trampling by humans or other animals. Without the discovery of actual tools, the argument seemed likely to continue without resolution.

Now, those missing tools may have been found. In a talk at the annual meeting of the Paleoanthropology Society here, archaeologist Sonia Harmand of Stony Brook University in New York described the discovery of numerous tools at the site of Lomekwi 3, just west of Lake Turkana in Kenya, about 1000 kilometers from Olduvai Gorge. In 2011, Harmand’s team was seeking the site where a controversial human relative called Kenyanthropus platyops had been discovered in 1998. They took a wrong turn and stumbled upon another part of the area, called Lomekwi, near where Kenyanthropus had been found. The researchers spotted what Harmand called unmistakable stone tools on the surface of the sandy landscape and immediately launched a small excavation.

More tools were discovered under the ground, including so-called cores from which human ancestors struck off sharp flakes; the team was even able to fit one of the flakes back to its original core, showing that a hominin had crafted and then discarded both core and flake in this spot. The researchers returned for more digging the following year and have now uncovered nearly 20 well-preserved flakes, cores, and anvils apparently used to hold the cores as the flakes were struck off, all sealed in sediments that provided a secure context for dating. An additional 130 pieces have also been found on the surface, according to the talk.

“The artifacts were clearly knapped [created by intentional flaking] and not the result of accidental fracture of rocks,” Harmand told the meeting. Analysis of the tools showed that they had been rotated as flakes were struck off, which is also how Oldowan tools were crafted. The Lomekwi tools were somewhat larger than the average Oldowan artifacts, however. Dating of the sediments using paleomagnetic techniques—which track reversals in Earth’s magnetic field over time and have been used on many hominin finds from the well-studied Lake Turkana area—put them at about 3.3 million years old.

Although very recent research has now pushed back the origins of the genus Homo to as early as 2.8 million years ago, the tools are too old to have been made by the first fully fledged humans, Harmand said in her talk. The most likely explanation, she concluded, was that the artifacts were made either by australopithecines similar to Lucy or by Kenyanthropus. Either way, toolmaking apparently began before the birth of our genus. Harmand and her colleagues propose to call the new tools the Lomekwian technology, she said, because they are too old and too distinct from Oldowan implements to represent the same technology.

Researchers who have seen the tools in person are enthusiastic about the claim. The finds are “very exciting,” says Alison Brooks, an anthropologist at George Washington University in Washington, D.C. “They could not have been created by natural forces … [and] the dating evidence is fairly solid.” She agrees that the tools are too early to have been made by Homo, suggesting that “technology played a major role in the emergence of our genus.”

The claim also looks good to paleoanthropologist Zeresenay Alemseged of the California Academy of Sciences here, a leader of the team that found cut marks on the Dikika animal bones. (At the meeting, another team member presented new arguments for the cut marks’ authenticity.) “With the cut marks from Dikika we had the victim” of the stone tools, Alemseged says. “Harmand’s discovery gives us the smoking gun.”