Integrating Mechanical and Ergonomic Research within Functional and Morphological Analyses of Lithic Cutting Technology: Key Principles and Future Experimental Directions

Abstract

The functional value of a stone tool is principally in its ability to cut, split, or otherwise deform material. The relative efficiency with which stone tools undertake cutting processes has been a point of interest to lithic archaeologists for decades, with many linking aspects of tool morphology to functional performance. Many of the questions asked by stone tool research are, however, pertinent to other disciplines. This includes mechanical engineering and ergonomic sciences where there is a substantial amount of research dedicated to understanding the mechanics of cutting and the influence exerted by tool-form attributes during use. These investigations therefore have valuable insights for lithic archaeology and our understanding of the variables that would have been influencing stone tool use in past populations. Here, the value of mechanical and ergonomic research to lithic archaeology is analyzed, key morphological and mechanical principles central to the determination of a stone tool's cutting efficiency are reviewed, and the need for future experiments that investigate these principles within archaeological contexts is highlighted.

Hand grip diversity and frequency during the use of Lower Palaeolithic stone cutting-tools

“…Analysis of each tool-use event provided a record of the grips used to manipulate the stone tool, how long individual grips were used, and a total overall record of how long each tool-use event lasted. Given that individual tools were used for varying lengths of time due to external variables, such as biometric differences across participants or differing tool-use contexts (Key andLycett, 2011, 2017c, in press;Merritt, 2012Merritt, , 2016), it was not always possible to directly compare time records across different tool types and forms. Therefore, we calculated an additional variable, 'Percentage of Use' (PoU), which was the percentage of time that a specific hand grip was used relative to the overall time record for which that tool was used.…”

“…In addition, it has been well-documented that, relative to flakes, handaxes display higher standardisation in form, with a series of morphological traits conforming to produce a general handaxe bauplan (sensu Lycett and Gowlett, 2008) describing their form (Gowlett, 2015). This includes their shape and the presence of a 'globular butt' (Gowlett, 2006), both of which have been previously linked to their ease of manipulation during use (Kleindienst and Keller, 1976;Jones, 1994;Grosman et al, 2011;Key et al, 2016). Here, handaxe 3D shape was recorded using a size-adjusted (scale-free) dataset of 29 morphometric variables from each of the 500 handaxes.…”

“…The majority of cutting behaviours in Experiments 1-3 were slicing or sawing actions, whereby a tool's edge is drawn longitudinally across a material while simultaneously providing force into the cut substrate (Key, 2016). Further, cutting actions were required in multiple angular, horizontal and vertical plains, thereby more accurately replicating varied actualistic conditions (particularly in Experiments 2 and 3).…”

Biometric variables predict stone tool functional performance more effectively than tool‐form attributes: a case study in handaxe loading capabilities

“…; Collins ; Jobson ; Key and Lycett ; Prasciunas ; Walker ). ‘Loading’ is a crucial variable in the performance of a cutting tool (Atkins ; Key ), being directly related to the generation of ‘cutting stress’ (force per unit area). Presented here are data investigating the comparative influence that biometric variables and tool‐form variables have on the loading capabilities of Acheulean handaxes.…”

“…The greater the stress, the more likely it is that material bonds will be broken (Atkins ). The morphology of a stone tool's cutting edges (e.g., edge radii, angle, curvature) influences cutting stress by altering the amount (area) and morphology of the edge in contact with the material being cut and, moreover, how forces are distributed through this edge (Ackerly ; Atkins ; Key ). Overall tool‐size and shape attributes, meanwhile, affect the ergonomic nature of the tool, how precisely it may be applied during cutting and how much force is required to stabilize the tool in the hand, as well as the length of utilizable cutting edge (Hall ; Key et al .…”