Intentional heat treating of toolstone has been documented to have begun at least by 70 K BP; however, the advantages of such treatment have been debated for decades. There are two schools of thought with regard to its purpose. One, is that it merely reduces the force required for flake propagation. A second is that it also alters flake morphological properties. We systematically tested these hypotheses by generating flakes from cores exposed to three different temperatures (ambient, 300 °C, and 350 °C) using automated propagation procedures that bypassed any human agency. While the force propagation magnitude is altered by heat treatment, the flakes were not. We examined these flakes according to nine measures of morphology. None differed significantly or systematically within the three categories. While our results confirm that heat treatment does reduce the force needed for flake propagation, they also demonstrate that such treatment has no significant effect on major morphological aspects of flake form.

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Identifying stone tool production techniques in the archaeological record can inform on prehistoric economy, time budgets, shared cultural practices, and the spatiotemporal occurrence of technological innovations and adaptations. The pressure flaking technique is one such innovation that appears on every continent Homo sapiens colonized. Pressure flaking has long been associated with the ability of flintknappers to produce small, regularly shaped flakes that were used to maintain particular edge shapes and resharpen dull tool edges with minimal loss of raw material. Despite the importance of pressure flaking, a method for supporting the identification of pressure flakes in the archaeological record is lacking. Here, we present a stone tool replication experiment that statistically compares flakes derived from bifacial pressure flaking and soft hammer percussion flaking. Our analyses show that pressure flakes are on average lighter, shorter, narrower, and thicker than soft hammer percussion flakes. Discriminant analyses indicate that pressure flakes can be correctly classified at a rate of 70 percent in a mixed sample. Furthermore, our findings validate the assumption that pressure flakes are less variable in form compared to soft hammer percussion flakes. Based on our results, we suggest quantitatively reevaluating the presence of pressure flaking in the global archaeological record.

Identifying stone tool production techniques in the archaeological record can inform on prehistoric economy, time budgets, shared cultural practices, and the spatiotemporal occurrence of technological innovations and adaptations. The pressure flaking technique is one such innovation that appears on every continent Homo sapiens colonized. Pressure flaking has long been associated with the ability of flintknappers to produce small, regularly shaped flakes that were used to maintain particular edge shapes and resharpen dull tool edges with minimal loss of raw material. Despite the importance of pressure flaking, a method for supporting the identification of pressure flakes in the archaeological record is lacking. Here, we present a stone tool replication experiment that statistically compares flakes derived from bifacial pressure flaking and soft hammer percussion flaking. Our analyses show that pressure flakes are on average lighter, shorter, narrower, and thicker than soft hammer percussion flakes. Discriminant analyses indicate that pressure flakes can be correctly classified at a rate of 70 percent in a mixed sample. Furthermore, our findings validate the assumption that pressure flakes are less variable in form compared to soft hammer percussion flakes. Based on our results, we suggest quantitatively reevaluating the presence of pressure flaking in the global archaeological record.