The Rules are the Rules. Consistency of Drivers of Flake Size and Shape in Mechanical Flaking Experiments

Lithic flakes are central to Paleolithic assemblages, and their variability provides key insights into stone-tool technology, decision making, and hominin motor control. Mechanical flaking experiments isolate the main drivers of flake size and shape, but most have used glass plates or cuboid cores with Levallois-like surfaces. These standardized forms have clarified relationships among flake mass, platform depth, angle of blow, exterior platform angle, and force. Whether these findings generalize to markedly different core morphologies remains uncertain. To evaluate this, we conducted controlled mechanical experiments using glass hemispheres that approximate Oldowan pebble cores, producing 177 flakes under systematic variation in platform depth and angle of blow. Attribute analysis and 3D landmarking were used to assess flake features and their fit to existing models. The results show strong consistency with previous experiments, indicating that principles derived from standardized cores extend to hemispherical morphologies and across Paleolithic contexts.