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

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.

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.

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.

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.