Raw material selectivity in Lower Paleolithic shaped stone ball production: Experimental research

Shaped stone balls are ubiquitous in Oldowan and Acheulian sites worldwide. Despite years of research, very little is known about the shaping process of these items. A comprehensive literary review indicates variability in the types of rocks from which these items were shaped. At a number of sites, however, selectivity in the choice of materials used to make the balls is of note, with carbonate rocks (usually limestone) being preferred over flint and quartz. Do certain qualities of limestone affect the production process of stone balls? Is this selectivity related to their function? And do different rock types affect the development of macro detachments visible on the archaeological items? We explored these questions through a series of experiments, during which stone balls were shaped from different materials and then used for bone breaking. Their active edges (ridges) were documented before and after use. The results show that limestone is a preferred raw material for the peripheral knapping of stone balls because it allows better control of the knapping process, which prevents the balls from splitting. All the tools, however, were effective for intensive use, large detachments were not formed during bone breaking activities, and no differences were recorded between the different rock types in this respect. We thus suggest that the large detachments visible on the archaeological items are deliberate removals that were part of the peripheral shaping process, and following, that these items might have been desired tools rather than by-products of functional activity. It seems that in this process, selectivity of raw materials reflects an informed decision which may have become a cultural norm that was preserved for hundreds of thousands of years.