Considerations in the application of 3DGM to stone artifacts with a focus on orientation error in bifaces

Abstract Stone artifacts are the most abundant vestiges of hominin behavior for much of human evolutionary history. Our understanding of the relevance of stone artifacts to human behavioral evolution is driven largely by our ability to document and analyze stone artifact form (artifact size and shape). Three-dimensional geometrics morphometrics (3DGM) offers a set of high-resolution statistical shape analysis tools, traditionally used in biological studies, which are potentially useful in this endeavor. However, 3DGM has thus far only been applied successfully to a limited range of stone artifact forms. Due to the unique morphological characteristics of stone artifacts and the substantial variability in form within many types, there are a number of potential pitfalls in adapting 3DGM for usage in stone artifact analyses. In this chapter, some very basic considerations in the application of 3DGM to stone artifacts are discussed. The issue of artifact orientation poses a significant and unique hurdle in stone artifact forms with few geometrically correspondent features, and is thus given special attention. An assemblage of landmark configurations of bifacial tools (points or handaxes) is simulated. Portions of this assemblage are then manipulated in terms of their orientation, to add error to the dataset, and to illustrate the potential effects of orientation error when applying 3DGM to actual archeological assemblages.