A geometric morphometric relationship predicts stone flake shape and size variability

Abstract

The archaeological record represents a window onto the complex relationship between stone artefact variance and hominin behaviour. Differences in the shapes and sizes of stone flakes-the most abundant remains of past behaviours for much of human evolutionary history-may be underpinned by variation in a range of different environmental and behavioural factors. Controlled flake production experiments have drawn inferences between flake platform preparation behaviours, which have thus far been approximated by linear measurements, and different aspects of overall stone flake variability (Dibble and Rezek J Archaeol Sci 36:1945-1954 Lin et al. Am Antiq 724-745, 2013; Magnani et al. J Archaeol Sci 46:37-49, 2014; Rezek et al. J Archaeol Sci 38:1346-1359, 2011. However, when the results are applied to archaeological assemblages, there remains a substantial amount of unexplained variability. It is unclear whether this disparity between explanatory models and archaeological data is a result of measurement error on certain key variables, whether traditional analyses are somehow a general limiting factor, or whether there are additional flake shape and size drivers that remain unaccounted for. To try and circumvent these issues, here, we describe a shape analysis approach to assessing stone flake variability including a newly developed three-dimensional geometric morphometric method ('3DGM'). We use 3DGM to demonstrate that a relationship between platform and flake body governs flake shape and size variability. Contingently, we show that by using this 3DGM approach, we can use flake platform attributes to both (1) make fairly accurate stone flake size predictions and (2) make relatively detailed predictions of stone flake shape. Whether conscious or instinctive, an understanding of this geometric relationship would have been critical to past knappers effectively controlling the production of desired stone flakes. However, despite being able to holistically and accurately incorporate three-dimensional flake variance into our analyses, the behavioural drivers of this variance remain elusive.

Ceramic Morphological Organisation in the Southern Caddo Area: The Clarence H. Webb Collections

“…For research designs that incorporate questions associated with more complex geometry, 3D landmark-based approaches may be more appropriate. Examples from the literature include the development of novel tools and applications (Lycett et al, 2006), and cover a broad range of artefact categories including projectile points (Shott, 2011;Shott & Trail, 2010), bifaces (Archer & Braun, 2010;Archer et al, 2015Archer et al, , 2016, percussive tools (Caruana et al, 2014), flake scars (Sholts et al, 2012), flake tools (Archer et al, 2017), handaxes (Lycett, 2009;Lycett et al, 2010Lycett et al, , 2015Lycett & von Cramon-Taubadel, 2013;Wang et al, 2012), and Caddo ceramics (Selden Jr. et al, 2014). This study enlists the variation that occurs within a single plane for an aggregated sample of Caddo bottles; however, 3D data were required to identify the widest vessel profile.…”

The Variability of the Keilmesser-Concept: a Case Study from Central Germany

“…In contrast to Elliptical Fourier Analysis of 2D outlines, which has already been applied to late Middle Paleolithic stone tools (Iovita 2009;Serwatka 2015), 3DGM is more suitable for the backed asymmetric tools in question, as the 3D curves cover additionally the thickness and extension of the base and back (for the application of related 3D EFA, see e.g., Chacón et al 2016). Moreover, among other studies based on processing 3D scans (e.g., Archer et al 2017;Grosman et al 2008;Lin et al 2010;Morales et al 2015a;Morales et al 2015b), 3DGM has been successfully applied to bifacial stone artifacts, namely Stillbay points of the southern African MSA (Archer 2016;Archer et al 2015Archer et al , 2016.…”

Use and Multifactorial Reconciliation of Uniface Reduction Measures: A Pilot Study at the Nobles Pond Paleoindian Site

“…Evaluated against experimental controls and relevant archaeological data, all measures of estimated reduction show some error or uncertainty. This is true of analytical measures generally, certainly of reduction measures devised elsewhere (e.g., Archer et al 2016; Davis and Shea 1998; Dibble and Rezek 2009; Eren et al 2005; Hiscock and Clarkson 2005; Shott et al 2000). None is a panacea.…”

“…Ideally, such experiments also should include 3D digital artifact models at all stages of work from flake blank through modification for hafting and reduction from resharpening at each subsequent retouch episode. Archer and colleagues (2016) used geometric morphometrics to predict overall flake-blank size and shape from landmarked proximal segments, and failed to detect any influence of core surface preparation, angle of blow, or other variables that are difficult if not impossible to measure. Unfortunately, their study appeared after this study was completed, but their approach should be tested in future experiments.…”