The ancient stone tool industry of our early ancestors was just pushed deeper back in time, based on recent findings near the western shore of Lake Turkana in Kenya. Tools dating to over 3 million years ago - some 700,000 years earlier than previous finds - indicate the technology arose even before the genus Homo roamed the planet.

"Immediately, I knew that we had found something very special," says Sonia Harmand, a research associate professor at Stony Brook University, New York. "I knew these were stone tools, and very old. It was very exciting."

After the first tool was discovered, Dr. Harmand and co-leader of the project, Jason E. Lewis, were able to trace the scattered artifacts to a nearby hill, which fortunately contained datable volcanic sediments. The intentionally knapped stones were dated to 3.3 million years and may have been used for butchering meat. The big question that remains is, who made them?

Up to this point, the earliest stone tools dated to 2.6 million years and were attributed to Homo habilis, who wandered the dusty plains of Ethiopia during this same period. But the new dates push stone tool production to a period that predates habilis, which will require paleoanthropologists to reevaluate their theories.

"These tools shed light on an unexpected and previously unknown period of hominin behavior, and can tell us a lot about cognitive development in our ancestors that we can't understand from fossils alone," Harmand says. "Our finding disproved the longstanding assumption that Homo habilis was the first tool maker."

For now, likely candidates include the Australopithecines, the genus represented by the famous "Lucy" skeleton, discovered in 1974 at the site of Hadar, Ethiopia by a young Donald Johanson.

Although the new dates are exciting, they are not exactly unexpected. The 2.6 million year old tools, although rudimentary by today's standards, already exhibited a level of refinement that indicates they had been around for some time. And even at 3.3 million years, these most recent finds may eventually be supplanted by a more ancient industry.