"How Handy was early hominin 'know-how'?" An experimental approach exploring efficient early stone tool use.

Objectives: The appearance of early lithic industries has been associated with the gradual development of unique biomechanical and cognitive abilities in hominins, including human-like precision grasping and basic learning and/or communicating capacities. These include tools used for activities exclusively associated with hominin contexts (cutting flakes) and hammerstones utilized for behaviors shared with non-human primates (e.g., nut-cracking). However, no previous experimental research has focused on comparing the factors affecting efficiency between these two key behavioral patterns and their evolutionary implications.

Materials and methods: Here, we address this gap with an experimental design involving participants with varying tool-related experience levels (i.e., no experience, theoretical-only experience, and extensive practical knapping expertise) to monitor their success rates, biometrics, and surface electromyography (sEMG) recordings from eight important hand and forearm muscles.

Results: Our results showed that practical experience had a substantial impact on flake-cutting efficiency, allowing participants to achieve greater success rates with substantially less muscle effort. This relationship between success rates and muscle effort was not observed for the nut-cracking task. Moreover, even though practical experience did not significantly benefit nut-cracking success, experts exhibited increased rates of self-improvement in that task.

Discussion: Altogether, these experimental findings suggest that the ability to practice and retain tool-using knowledge played a fundamental role in the subsistence strategies and adaptability of early hominins, potentially providing the cognitive basis for conceptualizing the first intentional tool production strategies.