A round stone excavated at Israel’s Tabun Cave in the 1960s represents the oldest known grinding or rubbing tool, say researchers who scrutinized the 350,000-year-old find.
The specimen marks a technological turn to manipulating objects with wide, flat stone surfaces, say Ron Shimelmitz, an archaeologist at the University of Haifa in Israel, and his colleagues. Up to that time, stone implements had featured thin points or sharp edges. Microscopic wear and polish on a worn section of the Tabun stone resulted from it having been ground or rubbed against relatively soft material, such as animal hides or plants, the scientists conclude in the January Journal of Human Evolution.
Similar stones bearing signs of abrasion date to no more than around 200,000 years ago. Specific ways in which the Tabun stone was used remain a mystery. By around 50,000 years ago, though, human groups were using grinding stones to prepare plants and other foods, Shimelmitz says.
The team compared microscopic damage on the Tabun stone to that produced in experiments with nine similar stones collected near the cave site. Archaeology students forcefully ran each of the nine stones back-and-forth for 20 minutes over different surfaces: hard basalt rock, wood of medium hardness or a soft deer hide. Those applied to deer hide displayed much in common with the business end of the ancient stone tool, including a wavy surface and clusters of shallow grooves.
It’s unclear which evolutionary relatives of Homo sapiens — whose origins go back about 300,000 years (SN: 6/7/17) —made the Tabun tool, Shimelmitz says. Other innovations around the same time included regular fire use (SN: 4/2/12).