Biomechanical demands of percussive techniques in the context of early stone toolmaking

Abstract

Recent discoveries in archaeology and palaeoanthropology highlight that stone tool knapping could have emerged first within the genera Australopithecus or Kenyanthropus rather than Homo . To explore the implications of this hypothesis determining the physical demands and motor control needed for performing the percussive movements during the oldest stone toolmaking technology (i.e. Lomekwian) would help. We analysed the joint angle patterns and muscle activity of a knapping expert using three stone tool replication techniques: unipolar flaking on the passive hammer (PH), bipolar (BP) flaking on the anvil, and multidirectional and multifacial flaking with free hand (FH). PH presents high levels of activity for Biceps brachii and wrist extensors and flexors. By contrast, BP and FH are characterized by high solicitation of forearm pronation. The synergy analyses depict a high muscular and kinematic coordination. Whereas the muscle pattern is very close between the techniques, the kinematic pattern is more variable, especially for PH. FH displays better muscle coordination and conversely lesser joint angle coordination. These observations suggest that the transition from anvil and hammer to freehand knapping techniques in early hominins would have been made possible by the acquisition of a behavioural repertoire producing an evolutionary advantage that gradually would have been beneficial for stone tool production.

Identifying intentional flake production at the dawn of technology: A technological and 3D geometric morphometric study

“…This variation is associated with larger passive hammer flakes compared to both freehand and SoS flakes. The same pattern is observed between archaeological examples of passive hammer and freehand flakes (Braun et al, 2019;de la Torre and Mora, 2005;Delagnes and Roche, 2005;Harmand et al, 2015), and may be associated with an increased application of force during this knapping technique (Macchi et al, 2021). There are no statistical differences between SoS and freehand flake dimensions.…”

Beyond the genus stereotype. Who were the first toolmarkers in Africa? Crossed views between archaeology and anatomy

“…Macchi and co-authors show that muscular demands are similar for passive hammer, bipolar, and free-hand percussion techniques, but that kinematic patterns are more variable. It is interesting to note that free-hand percussion is differentiated from the other two techniques, with more complex motor control demands (Macchi et al, 2021). Furthermore, in order to evaluate the prehensile abilities of a contemporary hominin from the Lomekwi site, a musculoskeletal model of the hand of Australopithecus afarensis was developed by Domalain and co-authors (Domalain et al, 2017).…”

Form, function and evolution of the human hand

“…Both methods were also used during the Oldowan, as well as free‐hand direct‐hammer percussion (Schick & Toth, 2006; Semaw et al, 2009; Stout et al, 2010). Limited experimental biomechanical information (i.e., kinetics, kinematics, EMG) is available on passive‐hammer and bipolar techniques (Macchi et al, 2021 is the exception), and even less is known about the biomechanics of the hand during these behaviors. Musculoskeletal modeling of the hand of Au.…”