Meeting Abstract
Tool-assisted percussion was, and still remains, a key way in which hominins alter their environment. Tool-assisted percussion is not uniquely hominin, as a few wild populations of bearded capuchin monkeys, long-tailed macaques, and chimpanzees habitually use percussive tools. Knowing species-specific differences in percussive skills allows us to address fundamental questions about the evolution of tool-assisted percussion in hominins. In the present study, we quantified percussive skill in wild bearded capuchin monkeys, Sapajus libidinosus, novice humans (scientists), and expert humans (local residents) at Fazenda Boa Vista, Piauí, Brazil, as they used anvil-and-hammer tools to crack open tucum palm, Astrocaryum spp. nuts. Astonishingly, the monkeys outperformed the novice humans, and the expert humans outperformed the monkeys, in terms of the number of strikes to crack open a single intact nut. The monkeys hit a nut repeatedly with a moderate force (i.e., by not exceeding a threshold) and modulated the force of each hit on the basis of the condition of the nut (i.e., the development of a fracture/crack) following the preceding hit. The novice humans, although they hit with a force comparable to that which the monkeys used, had to hit the nut a large number of times to extract the kernel. The expert humans hit with a force greater than that which the monkeys used and extracted the kernel of the nut in just a few hits. Together these results suggest that nut-cracking skill in both bearded capuchin monkeys and humans are embodied, with actions grounded in the musculoskeletal system and perception–action routines, and not anticipatory, with actions divorced from the task and environment. Thus, hypotheses linking skillful percussion uniquely to hominins demand reassessment.
