How do we know when humans first started making tools?

We know when tools began because stone lasts, and layers of volcanic ash around it can be dated. For decades the oldest known tools were the Oldowan kind. They are simple sharp flakes knocked off one stone with another. Louis Leakey first found them at Olduvai Gorge, Tanzania, in the 1930s. The oldest ones, from Nyayanga in Kenya, are about 2.9 million years old.

These tools were long credited to Homo habilis, the "handy man". It seemed neat: our genus, Homo, was the toolmaker. But the evidence is thin. Habilis is known from only two badly broken skeletons. And no one can say for sure which species made the first Oldowan tools.

Then, in 2011, a team near Lake Turkana, Kenya, took a wrong turn. They ended up at an unexplored site, later called Lomekwi 3. There they found stone tools 3.3 million years old. That is about 500,000 years before the genus Homo existed. So the first toolmakers were probably older hominins, such as australopithecines.

The Lomekwi makers chose big, heavy stones on purpose. The largest tool weighs 15 kilograms. One flake even fits back onto the stone it came from. What they used the tools for is still a mystery: the animal bones nearby show no cut marks.