Experimental Insights into the Cognitive Significance of Early Stone Tools.

Yinika Perston,Michael D Petraglia,Mark W Moore

doi:10.1371/journal.pone.0158803

Abstract

Stone-flaking technology is the most enduring evidence for the evolving cognitive abilities of our early ancestors. Flake-making was mastered by African hominins ~3.3 ma, followed by the appearance of handaxes ~1.75 ma and complex stone reduction strategies by ~1.6 ma. Handaxes are stones flaked on two opposed faces (‘bifacially’), creating a robust, sharp-edged tool, and complex reduction strategies are reflected in strategic prior flaking to prepare or ‘predetermine’ the nature of a later flake removal that served as a tool blank. These technologies are interpreted as major milestones in hominin evolution that reflect the development of higher-order cognitive abilities, and the presence and nature of these technologies are used to track movements of early hominin species or ‘cultures’ in the archaeological record. However, the warranting argument that certain variations in stone tool morphologies are caused by differences in cognitive abilities relies on analogy with technical replications by skilled modern stoneworkers, and this raises the possibility that researchers are projecting modern approaches to technical problems onto our non-modern hominin ancestors. Here we present the results of novel experiments that randomise flake removal and disrupt the modern stoneworker’s inclination to use higher-order reasoning to guide the stone reduction process. Although our protocols prevented goal-directed replication of stone tool types, the experimental assemblage is morphologically standardised and includes handaxe-like ‘protobifaces’ and cores with apparently ‘predetermined’ flake removals. This shows that the geometrical constraints of fracture mechanics can give rise to what appear to be highly-designed stoneworking products and techniques when multiple flakes are removed randomly from a stone core.

Highlights

If the archaeological traces could have been generated by simpler actions, or if the actions could have been organized by a simpler cognitive system, the simpler explanation must be favoured. ([1]:S12)PLOS ONE | DOI:10.1371/journal.pone.0158803 July 8, 2016Experimental Insights into Early Stone ToolsThe persistence of stone tool-making across sequential hominin species suggests that the hominin phenotype evolved alongside this technology [2, 3] and changes in toolmaking through time and across species is evidence of cognitive evolution [4,5,6,7,8]
Cognitive ability is inferred from the regularity of geometrical attributes of artefact types because metrical conformity suggests greater attention to design and more advanced cognition [8, 11,12,13,14,15,16,17]
Core reduction was guided by an imprecise mental visualisation, and no concept of predetermining flake shape by prior flaking [94]

Summary

Introduction

If the archaeological traces could have been generated by simpler actions, or if the actions could have been organized by a simpler cognitive system, the simpler explanation must be favoured. ([1]:S12). In cases where such a platform was randomly selected, and the flake successfully removed, core forms were produced that possessed morphological attributes commonly attributed to deliberate ‘predetermination’ of the resulting flake (Fig 12) This occurred 18 times in 11 of the 59 experiments, or 1.6% of the total number of blows (Table 15). A minimum of 10 blows preceded the configuration for predetermination, but this result is partly because, by convention (e.g., [82, 85, 87, 88]), the ‘predetermination’ configuration was recorded only when the relevant core mass was created by prior flake removals (and not by natural configurations on cobbles or pre-existing dorsal scar configurations on flake blanks) On average, this point was reached in the final 20% of core reduction, calculated relative to total blow counts and mass removal (Table 15). The removal of most redirecting flakes—and nearly a quarter of contact removal flakes—created a burin scar on the core (Table 19)

Findings

Discussion

Conclusion