A 35,000-year-old stone ax discovered in northern Australia is the oldest known tool with ground edges, researchers reported on Saturday (Nov. 6).
Humans' hominid ancestors have been using stone tools for 3.4 million years. But the use of grinding to sharpen stone tool edges didn't come until much later, after Homo sapiens arrived on the scene. Previously, the oldest ground tools were found in northern Australia and Japan and dated to 22,000 to 30,000 years ago.
The ground-edge ax was uncovered in May 2010 at Nawarla Gabarnmang, a site famous for Aboriginal rock art.
The ax was found 25 miles (40 kilometers) from the quarry where the rock was sourced, the researchers report in the December issue of the journal Australian Archaeology.
Before grounding tools, axes would have been less efficient, as bumps and other rough patches would have created friction, impeding cutting of the wood, said David Bruno, a Monash University archaeologist and a member of the team that made the discovery.
"In this sense edge grinding is a significant technological innovation that increases the efficiency of the tool," Bruno told LiveScience. "It is a technological innovation on par with the invention of the bow and arrow."
The finding suggests Australia was an important spot of technological innovation so long ago, he added.
"Once ground-edge axes were invented it caused the existence of new objects with high investment in labor, usually involving a raw material type obtained from limited locales only, and therefore generated a new kind of valued object that could be traded," Bruno explained. "The effect of this was an enhanced social momentum of giving valued objects that increased an ethos of reciprocity and symbolic value. In this sense it generated or intensified a social evolutionary process of a social process that we are familiar with in our own lives today."