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Abstract: The Acheulean industrial complex combines technological variability with continuity on a scale unparalleled by more recent industries. Acheulean variability includes a widely recognized increase in biface refinement from the Early to Late Acheulean, however the specific timing and technological nature of this shift remain unclear as do its behavioral, cognitive, and evolutionary implications. To investigate this topic, we examined lithic collections from the early Middle Pleistocene Acheulean site of Boxgrove for evidence of the use of platform preparation as a biface thinning technique. To aid in the identification and assessment of platform preparation, Boxgrove artifacts were compared with experimental products of Inexperienced, Novice, and Expert stone knappers. Results demonstrate the technologically efficacious use of platform preparation among the Boxgrove toolmakers ∼500 thousand years ago, providing the first direct evidence of this technique in the Acheulean. The use of platform preparation in bifacial thinning increases the complexity of toolmaking action sequences and has implications for understanding the neurocognitive substrates, social transmission, and spatiotemporal distribution of Late Acheulean technology. [Copyright &y& Elsevier]

Abstract: Inter-site technological variation in the archaeological record is one of the richest potential sources of information about Plio-Pleistocene hominid behavior and evolution. However, appropriate methods for describing and comparing Oldowan assemblages have yet to be agreed upon, and interpretation of the early record remains highly controversial. Particularly salient is disagreement over whether the Oldowan is a single technological phenomenon or is more accurately divided into multiple regional and/or chronological traditions, perhaps including a less developed Pre-Oldowan phase in the late Pliocene. Some of this disagreement reflects theoretical and methodological differences between research traditions and some is more directly evidential. Here we present a framework for describing and interpreting Oldowan variation and apply it to three Pliocene assemblages (EG-10, EG-12, and OGS-7) from Gona, all dated to c. 2.6 million years (Ma). Results indicate proficient knapping and a full range of Oldowan reduction strategies in these earliest known occurrences, consistent with the idea of an Oldowan “technological stasis” from 2.6–1.6Ma. Patterns of variation in raw material selection and predominant reduction strategy at each site clearly indicate the importance of cultural transmission in the Oldowan, but confounding ecological and economic variation continue to render interpretation in terms of multiple tool making traditions or species inappropriate. We propose that cultural transmission and ecological adaptation should be recognized as complementary, rather than mutually exclusive, mechanisms in future attempts to explain Oldowan technological variation. [Copyright &y& Elsevier]

Abstract: Published evidence of Oldowan stone exploitation generally supports the conclusion that patterns of raw material use were determined by local availability. This is contradicted by the results of systematic studies of raw material availability and use among the earliest known archaeological sites from Gona, Afar, Ethiopia. Artifact assemblages from six Pliocene archaeological sites were compared with six random cobble samples taken from associated conglomerates that record pene-contemporaneous raw material availability. Artifacts and cobbles were evaluated according to four variables intended to capture major elements of material quality: rock type, phenocryst percentage, average phenocryst size, and groundmass texture. Analyses of these variables provide evidence of hominid selectivity for raw material quality. These results demonstrate that raw material selectivity was a potential component of Oldowan technological organization from its earliest appearance and document a level of technological sophistication that is not always attributed to Pliocene hominids. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Many of the behavioral capacities that distinguish humans from other primates rely on fronto-parietal circuits. The superior longitudinal fasciculus (SLF) is the primary white matter tract connecting lateral frontal with lateral parietal regions; it is distinct from the arcuate fasciculus, which interconnects the frontal and temporal lobes. Here we report a direct, quantitative comparison of SLF connectivity using virtual in vivo dissection of the SLF in chimpanzees and humans. SLF I, the superior-most branch of the SLF, showed similar patterns of connectivity between humans and chimpanzees, and was proportionally volumetrically larger in chimpanzees. SLF II, the middle branch, and SLF III, the inferior-most branch, showed species differences in frontal connectivity. In humans, SLF II showed greater connectivity with dorsolateral prefrontal cortex, whereas in chimps SLF II showed greater connectivity with the inferior frontal gyrus. SLF III was right-lateralized and proportionally volumetrically larger in humans, and human SLF III showed relatively reduced connectivity with dorsal premotor cortex and greater extension into the anterior inferior frontal gyrus, especially in the right hemisphere. These results have implications for the evolution of fronto-parietal functions including spatial attention to observed actions, social learning, and tool use, and are in line with previous research suggesting a unique role for the right anterior inferior frontal gyrus in the evolution of human fronto-parietal network architecture. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]