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Stone-tool making is an ancient human skill thought to have played a key role in the bio-cultural co-evolutionary feedback that produced modern brains, culture, and cognition. To test the proposed evolutionary mechanisms underpinning this hypothesis we studied stone-tool making skill learning in modern participants and examined interactions between individual neurostructural differences, plastic accommodation, and culturally transmitted behavior. We found that prior experience with other culturally transmitted craft skills increased both initial stone tool-making performance and subsequent neuroplastic training effects in a frontoparietal white matter pathway associated with action control. These effects were mediated by the effect of experience on pre-training variation in a frontotemporal pathway supporting action semantic representation. Our results show that the acquisition of one technical skill can produce structural brain changes conducive to the discovery and acquisition of additional skills, providing empirical evidence for bio-cultural feedback loops long hypothesized to link learning and adaptive change., (© 2023. The Author(s).)

Stone tools provide some of the best remaining evidence of behavioral change over long periods, but their cognitive and evolutionary implications remain poorly understood. Here, we contribute to a growing body of experimental research on the cognitive and perceptual-motor foundations of stone toolmaking skills by using a flake prediction paradigm to assess the relative importance of technological understanding vs. accurate action execution in Late Acheulean-style handaxe production. This experiment took place as part of a larger, longitudinal study of knapping skill acquisition, allowing us to assemble a large sample of predictions across learning stages and in a comparative sample of experts. By combining group and individual-level statistical analyses with predictive modeling, we show that understanding and predicting specific flaking outcomes in this technology is both more difficult and less important than expected from previous work. Instead, our findings reveal the critical importance of perceptual motor skills needed to manage speed-accuracy trade-offs and reliably detach the large, invasive flakes that enable bifacial edging and thinning. With practice, novices increased striking accuracy, flaking success rates, and (to an extent) handaxe quality by targeting small flakes with acute platform angles. However, only experts were able to combine percussive force and accuracy to produce results comparable with actual Late Acheulean handaxes. The relatively intense demands for accurate action execution documented in our study indicate that biomechanical properties of the upper limb, cortical and cerebellar systems for sensorimotor control, and the cognitive, communicative, and affective traits supporting deliberate practice would all have been likely targets of selection acting on Late Acheulean toolmaking aptitude., Competing Interests: Conflict of interest The authors report no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Despite its theoretical importance, the process of stone tool-making skill acquisition remains understudied and poorly understood. The challenges and costs of skill learning constitute an oft-neglected factor in the evaluation of alternative adaptive strategies and a potential source of bias in cultural transmission. Similarly, theory and data indicate that the most salient neural and cognitive demands of stone tool-making should occur during learning rather than expert performance. Unfortunately, the behavioral complexity and extensive learning requirements that make stone knapping skill acquisition an interesting object of study are the very features that make it so challenging to investigate experimentally. Here we present results from a multidisciplinary study of Late Acheulean handaxe-making skill acquisition involving twenty-six naïve participants and up to 90 hours training over several months, accompanied by a battery of psychometric, behavioral, and neuroimaging assessments. In this initial report, we derive a robust quantitative skill metric for the experimental handaxes using machine learning algorithms, reconstruct a group-level learning curve, and explore sources of individual variation in learning outcomes. Results identify particular cognitive targets of selection on the efficiency or reliability of tool-making skill acquisition, quantify learning costs, highlight the likely importance of social support, motivation, persistence, and self-control in knapping skill acquisition, and illustrate methods for reliably reconstructing ancient learning processes from archaeological evidence., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Stone tools provide some of the most abundant, continuous, and high resolution evidence of behavioral change over human evolution, but their implications for cognitive evolution have remained unclear. We investigated the neurophysiological demands of stone toolmaking by training modern subjects in known Paleolithic methods ("Oldowan", "Acheulean") and collecting structural and functional brain imaging data as they made technical judgments (outcome prediction, strategic appropriateness) about planned actions on partially completed tools. Results show that this task affected neural activity and functional connectivity in dorsal prefrontal cortex, that effect magnitude correlated with the frequency of correct strategic judgments, and that the frequency of correct strategic judgments was predictive of success in Acheulean, but not Oldowan, toolmaking. This corroborates hypothesized cognitive control demands of Acheulean toolmaking, specifically including information monitoring and manipulation functions attributed to the "central executive" of working memory. More broadly, it develops empirical methods for assessing the differential cognitive demands of Paleolithic technologies, and expands the scope of evolutionary hypotheses that can be tested using the available archaeological record.