Two million years of flaking stone and the evolutionary efficiency of stone tool technology

Abstract

Temporal variability in flaking stone has been used as one of the currencies for hominin behavioural and biological evolution. This variability is usually traced through changes in artefact forms and techniques of production, resulting overall in unilineal and normative models of hominin adaptation. Here, we focus on the fundamental purpose of flaking stone-the production of a sharp working edge-and model this behaviour over evolutionary time to reassess the evolutionary efficiency of stone tool technology. Using more than 19,000 flakes from 81 assemblages spanning two million years, we show that greater production of sharp edges was followed by increased variability in this behaviour. We propose that a diachronic increase in this variability was related to a higher intensity of interrelations between different behaviours involving the use and management of stone resources that gave fitness advantages in particular environmental contexts. The long-term trends identified in this study inform us that the evolutionary efficiency of stone tool technology was not inherently in advanced tool forms and production techniques, but emerged within the contingencies of hominin interaction with local environments.

The results of lithic experiments performed on glass cores are applicable to other raw materials

“…The clear conclusion-both from our experiments and from comparison with archeological data-is that the EPA and PD predict flake size irrespective of the raw material-including glass. Our results show that the experiments performed on glass are valid and therefore generalizable not only to several other materials that were knapped in the past but that this also provides insights into significant aspects of prehistoric lithic assemblage variability (see also Lin et al 2013;Režek et al 2018). We showed that it takes different amounts of force to remove flakes of the same size (weight) made on materials of different properties.…”

“…A new experimental design, used first about 10 years ago (Dibble and Rezek 2009) and used again here, overcame some of these limitations by using glass cores that could be molded which allowed core surface configurations that yielded flakes that more closely resembled archeological ones. In itself, this new design helped to (Leader et al 2017) EPA, PD Flake weight, length/width, area/thickness, area/weight, usable edge, bulb length (Lin et al 2013) EPA, PD Usable edge (Režek et al 2018) EPA, PD, core morphology Flake shape (Rezek et al 2011) increase both the external and ecological validity of the experiment. The use of glass cores therefore maintained high internal validity due to the fact that all of the cores were molded to be identical in size and shape.…”

“…Over the course of numerous glass-core experiments, several independent variables were examined, including exterior platform angle, platform depth, hammer speed, force, angle of blow (Pelcin and Dibble 1995), core morphology (Rezek et al 2011), hammer type (Magnani et al 2014), and platform beveling (Leader et al 2017). The results of these experiments have helped to describe and quantify how knappers achieve particular results, with direct implications for interpreting the archeological record (Lin et al 2013;Režek et al 2018). While glass itself is highly amenable to percussion flaking, it still leaves the question as to the applicability and the validity of the results of these experiments to the kinds of raw materials actually knapped in the past.…”

Territoriality and the organization of technology during the Last Glacial Maximum in southwestern Europe

“…The chosen variables, and respective combinations, were based on the traditional parameters used in lithics attribute analysis [94,95] and the results of experimental studies available in the literature [74][75][76][77][96][97][98][99][100]. For example, controlled knapping experiments show that blank dimensions and shape are significantly affected by variations in exterior platform angles, platform depths, and platform preparation (e.g., faceting) [98,101]. Thus, by considering variables such as platform type and blank elongation (length/width ratio) as a set of interrelated variables, the way knappers differently exploited these variables can be assessed and compared across assemblages.…”

Introducing platform surface interior angle (PSIA) and its role in flake formation, size and shape

“…The EPA-PD model has been replicated in multiple ways, including experiments in the material sciences [6-8, 10, 20, 21] and in actual lithic assemblages (e.g. [18,22,23]). It is also argued that in certain conditions, EPA-PD has a stronger effect on flake size and shape than does core surface morphology [11,24].…”