A biomechanical investigation of the efficiency hypothesis of hafted tool technology

Abstract

The transition from hand-held to hafted tool technology marked a significant shift in conceptualizing the construction and function of tools. Among other benefits, hafting is thought to have given users a significant biomechanical and physiological advantage in undertaking basic subsistence tasks compared with hand-held tools. It is assumed that addition of a handle improved the (bio)mechanical properties of a tool and upper limb by offering greater amounts of leverage, force and precision. This controlled laboratory study compares upper limb kinematics, electromyography and physiological performance during two subsistence tasks (chopping, scraping) using hafted and hand-held tools. Results show that hafted tool use elicits greater ranges of motion, greater muscle activity and greater net energy expenditure (EE) compared with hand-held equivalents. Importantly, however, these strategies resulted in reduced relative EE compared with the hand-held condition in both tasks. More specifically, the hafted axe prompted use of two well-known biomechanical strategies that help produce larger velocities at the distal end of the limb without requiring heavy muscular effort, thus improving the tool's functional efficiency and relative energy use. The energetic and biomechanical benefits of hafting arguably contributed to both the invention and spread of this technology.

Challenges of dating quartz OSL samples with saturated grains: Lessons from single-grain analyses of low dose-rate samples from Victoria Falls, Zambia

“…These dating samples will provide chronological context for the archaeological findings and contribute to filling a large regional gap in our understanding of the timing of the transition from the Early to Middle Stone Age in this part of Africa (Barham et al, 2015). This period encompasses the evolution of Homo sapiens and transformative technological innovations (Coe et al, 2022), with the work at Victoria Falls providing a chronological framework to compare with the eastern and southern African archaeological records.…”

Evidence for the earliest structural use of wood at least 476,000 years ago

“…Woodworking was also a precursor for the Mid-Pleistocene invention of hafting, which increased efficiency of basic actions such as chopping and scraping 39 . The interlocking logs from BLB5 anticipate hafting's core concept: the combination of two or more parts to make a construction 40 , enhancing our understanding of the technical cognition of these toolmakers 11 .…”

Hafted technologies likely reduced stone tool-related selective pressures acting on the hominin hand

“…These studies only investigate a few Early Stone Age (ESA) and Lower Palaeolithic (LP) technologies, and although flakes and large cutting tool (LCT) bifaces characterise two to three million years of the archaeological record, there is little to no understanding of the selective pressures experienced by the hominin hand after the advent of the Middle Stone Age (MSA) and Middle Palaeolithic (MP) (although see 33 – 37 ). Simply, we have little evidence concerning the selective pressures experienced by the hominin hand after this point, despite there being major changes to how the hand interacts with these more complex, and often smaller 38 , tool types 26 , 39 .…”

“…Earlier non-hafted tool types were secured in the hand using precision grips, principally by the forceful flexion of the first distal phalanx, the second digit, and their recruitment in opposition to each other and digits three to five 17 , 22 , 40 . With the introduction of hafting, there was a trend towards more complex technologies and increased effectiveness during cutting, scraping, chopping, and piercing actions 36 , 37 , 39 , 41 . Simultaneously, there was a shift from the recruitment of precision grips to power grips (see 17 , 40 ), and in turn, a change in the musculoskeletal demands placed on the upper limb 36 , 37 , 42 .…”

“…With the introduction of hafting, there was a trend towards more complex technologies and increased effectiveness during cutting, scraping, chopping, and piercing actions 36 , 37 , 39 , 41 . Simultaneously, there was a shift from the recruitment of precision grips to power grips (see 17 , 40 ), and in turn, a change in the musculoskeletal demands placed on the upper limb 36 , 37 , 42 .…”