The application of 3D geometric morphometrics and laser surface scanning to investigate the standardization of cranial vault modification in the Andes

Cranial vault modification and the social significance of permanent body modification have long been an important topic of interest in Andean archaeology. While previous studies have enriched our understanding of these practices among prehistoric Andean populations, the introduction of 3D surface scanners and geometric morphometric methods in archaeology enable us to examine head-shaping practices in novel ways. In this pilot study, we used a NextEngine 3D Laser Surface Scanner to generate high resolution models of artificially modified crania from four archaeological sites dating to the Archaic (2300-1600 BCE), Formative (500 CE), late Middle Horizon/early Late Intermediate period (LIP) (750-1100 CE) in Chile and late LIP crania (circa 1350 CE) from central, highland Peru. Landmarks were recorded on the 3D digital models of crania and these data were analyzed to assess variation in vault shape within and between the samples. Results of the PCA analysis showed graphical separation of the annular, tabular erect, and some tabular oblique types even when gross morphological assessments proved challenging. We documented marked variation within the general modification type traditionally identified as tabular oblique, which suggests more detailed classifications within this type are needed. We also investigated how standardized (i.e., similar) particular cranial modification types were at each site, and results show that the coastal sites of Morro 1 and Playa Miller 7, and the highlands Huari-Vegachayoc Moqo site show higher levels of standardization than the other four samples. This study highlights the utility of 3D imaging and geometric morphometric methods for straightforward, objective assessments of cranial modification and levels of standardization within sites and within particular modification types. This has implications for understanding the broader social and cultural significance of this practice, such as whether there were shared cultural norms about how a head should be modified, which could have led to highly uniform modification practices and head shapes in the Andes.