A round stone excavated in Israel’s Tabun Cave in the 1960s represents the oldest grinding or scrubbing tool, say researchers who examined the find 350,000 years ago.
The specimen marks a technological turn in the manipulation of objects with wide, flat stone surfaces, say Ron Shimelmitz, an archaeologist at the University of Haifa in Israel, and his colleagues. Until that time, stone implements had thin tips or sharp edges. Scientists conclude in the January Journal of Human Evolution that microscopic wear and polishing of a worn section of Tabun stone was ground or rubbed against relatively soft material, such as animal skins or plants.
Similar stones with signs of abrasion date back no more than 200,000 years. The specific ways of using Tabun stone remain a mystery. About 50,000 years ago, however, human groups used grindstones to prepare plants and other foods, Shimelmitz says.
The team compared microscopic damage to the Tabun stone with that produced in experiments with nine similar stones collected near the cave site. Archeology students walked hard through each of the nine stones back and forth for 20 minutes on different surfaces: hard basalt rock, medium-hardwood, or soft deer skin. Those applied to deer skin were shown in common for the purpose of the old stone tool, including a wavy surface and clusters of shallow grooves.
It is unclear what evolutionary relatives of Homo sapiens – whose origins date back some 300,000 years (SN: 7/7/17) – made the Tabun tool, says Shimelmitz. Other innovations at the same time included the regular use of fire (SN: 2/04/12).