Outlining the knapping techniques: assessment of the shape and regularity of prismatic blades using elliptic Fourier analysis

Abstract

An important aspect of prismatic blade production is the choice of a knapping technique. This study tests the utility of elliptic Fourier analysis (EFA) for discriminating between different knapping techniques and offers a new perspective on blade variability. Our results indicate that there is an overlap in the outline shape and symmetry of individual blades produced by direct percussion, indirect percussion, and pressure debitage. Nevertheless, the EFA points out certain group-level differences regarding the shape and regularity of blade outlines and yields classification accuracy which is comparable to the previously proposed quantitative approaches for distinguishing blades produced by different knapping techniques. However, a more detailed analysis of technique-related factors shows that the emerging variability of blade outlines is more complex and that tripartite division might not always be suitable for reconstructing the past knapping behavior. We discuss the advantages and disadvantages of this method, and how it could complement the standard technological analysis in exploring and explaining blade variability.

Old Collection and New Insights: Technological Analysis of Obsidian Finds from the Late Neolithic Layers of Vinča-Belo Brdo

“…A detailed description of the EFA and the analytical protocol for the analysis of blade outlines are published elsewhere (Caple et al 2017;Hoggard et al 2019;Kuhl, Giardina 1982;Radinović, Kajtez 2021) and will be only briefly summarised here. Images of the dorsal sides of blades were edited and used for digitising the blade outlines.…”

“…To assess the issue of blade regularity more formally and explore other aspects of blade shape that are related to the knapping technique (Radinović, Kajtez 2021), the Elliptic Fourier Analysis was applied to the outlines of whole obsidian blades. The first three principal components, which explain a total of 94.3% of blade outline variability, are elongation, side-to-side symmetry, and tip-base width ratio (Fig.…”

“…However, certain blades have features that are not typical for direct percussion -they are somewhat more elongated than the majority of other obsidian blades from Belo Brdo; the maximal width of certain blades is located in the proximal part, which might be indicative of a pressure debitage (Fig. 9); e.g., Inizian et al 1999;Pelegrin 2006;Radinović, Kajtez 2021). Another indication for the possible use of pressure debitage for blade production is the presence of a regular bullet-shaped core (Fig.…”