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The use of stone hammers to produce sharp stone flakes—knapping—is thought to represent a significant stage in hominin technological evolution because it facilitated the exploitation of novel resources, including meat obtained from medium‐to‐large‐sized vertebrates. The invention of knapping may have occurred via an additive (i.e., cumulative) process that combined several innovative stages. Here, we propose that one of these stages was the hominin use of ‘naturaliths,’ which we define as naturally produced sharp stone fragments that could be used as cutting tools. Based on a review of the literature and our own research, we first suggest that the ‘typical’ view, namely that sharp‐edged stones are seldom produced by nonprimate processes, is likely incorrect. Instead, naturaliths can be, and are being, endlessly produced in a wide range of settings and thus may occur on the landscape in far greater numbers than archaeologists currently understand or acknowledge. We then explore the potential role this ‘naturalith prevalence’ may have played in the origin of hominin stone knapping. Our hypothesis suggests that the origin of knapping was not a ‘Eureka!’ moment whereby hominins first made a sharp flake by intention or by accident and then sought something to cut, but instead was an emulative process by hominins aiming to reproduce the sharp tools furnished by mother nature and already in demand. We conclude with a discussion of several corollaries our proposal prompts, and several avenues of future research that can support or question our proposal. 

Abstract Backing is a procedure for retouching a stone tool edge to an angle of or near 90°. Archaeologists have recorded backed lithic specimens in the Pleistocene and Holocene around the world. One prominent hypothesis for the occurrence of backing is that it increases a stone tool's adhesion relative to what it would have otherwise been with unmodified, sharp edges. We conducted a highly controlled semi‐static tensile test in which we assessed lithic specimens that possessed both a backed and a non‐backed edge, opposing each other. We hafted each specimen's backed and non‐backed edges to wood, and the bi‐hafted stone implement was then pulled apart using an Universal Instron Materials Tester, allowing for a direct ‘head‐to‐head’ comparison of the two edge types’ adhesive properties. Our tensile test results suggested no significant difference between backed and non‐backed edges in terms of adhesion, which does not support the hypothesis that backing increases a lithic specimen's adhesion. 

Lithic technologies dominate understanding of early humans, yet natural processes can fracture rock in ways that resemble artefacts made by Homo sapiens and other primates. Differentiating between fractures made by natural processes and primates is important for assessing the validity of early and controversial archaeological sites. Rather than depend on expert authority or intuition, the authors propose a null model of conchoidally fractured Antarctic rocks. As no primates have ever occupied the continent, Antarctica offers a laboratory for generating samples that could only have been naturally fractured. Examples that resemble artefacts produced by primates illustrate the potential of ‘archaeological’ research in Antarctica for the evaluation of hominin sites worldwide. 

Abstract Understanding prehistoric projectile weaponry performance is fundamental to unraveling past humans’ survival and the evolution of technology. One important debate involves how deeply stone-tipped projectiles penetrate a target. Theoretically, all things being equal, projectiles with smaller tip cross-sectional geometries should penetrate deeper into a target than projectiles with larger tip cross-sectional geometries. Yet, previous experiments have both supported and questioned this theoretical premise. Here, under controlled conditions, we experimentally examine fourteen types of stone-tipped projectile each possessing a different cross-sectional geometry. Our results show that both tip cross-sectional area (TCSA) and tip cross-sectional perimeter (TCSP) exhibit a strong, significant inverse relationship with target penetration depth, although TCSP’s relationship is stronger. We discuss why our experimental results support what is mathematically predicted while previous experiments have not. Our results are consistent with the hypothesis that when stone tip cross-sectional geometries become smaller over time in particular contexts, this evolution may be due to the selection of these attributes for increased penetration. 

In Late Pleistocene North America colonizing hunter-gatherers knapped and used Clovis fluted projectile points. During their expansion the size and shape of Clovis points changed significantly. Archaeologists know that cultural drift contributed to this variation, but is it possible that this single source could alone generate so much variation so quickly? We present the first of several experimental studies exploring whether Clovis size and shape variation results in performance differences, focusing here on how deeply different Clovis point forms penetrate a target. Our ballistics experiment demonstrates that seven different Clovis point forms penetrated the same target with different effectiveness. Even after tip cross-sectional perimeter is accounted for, there are significant differences in penetration depths between two of the point types. These results are consistent with the hypothesis that Clovis people in different times and places may have chosen specific attributes to provide them with a selective functional advantage.