Neural correlates of Early Stone Age toolmaking: technology, language and cognition in human evolution

TLDR

Archaeological and palaeontological evidence from the Early Stone Age shows parallel trends of brain expansion and technological elaboration over more than 2 Myr, yet the relationship between these trends remains controversial and poorly understood. The study presents positron emission tomography results of functional brain activation during experimental Oldowan and Acheulean toolmaking performed by expert subjects. PET imaging was used to assess brain activity while experts produced Oldowan and Acheulean tools, focusing on visuomotor coordination and hierarchical action organization. The findings reveal that advanced Acheulean toolmaking engages greater visuomotor coordination and hierarchical action organization, reflected by heightened activation of ventral premotor, inferior parietal, and right Broca’s‑area homologues, indicating shared neural substrates with language and supporting coevolutionary links between language, toolmaking, and cortical expansion.

Abstract

Archaeological and palaeontological evidence from the Early Stone Age (ESA) documents parallel trends of brain expansion and technological elaboration in human evolution over a period of more than 2 Myr. However, the relationship between these defining trends remains controversial and poorly understood. Here, we present results from a positron emission tomography study of functional brain activation during experimental ESA (Oldowan and Acheulean) toolmaking by expert subjects. Together with a previous study of Oldowan toolmaking by novices, these results document increased demands for effective visuomotor coordination and hierarchical action organization in more advanced toolmaking. This includes an increased activation of ventral premotor and inferior parietal elements of the parietofrontal praxis circuits in both the hemispheres and of the right hemisphere homologue of Broca's area. The observed patterns of activation and of overlap with language circuits suggest that toolmaking and language share a basis in more general human capacities for complex, goal-directed action. The results are consistent with coevolutionary hypotheses linking the emergence of language, toolmaking, population-level functional lateralization and association cortex expansion in human evolution.