Perdiz arrow points from Caddo burial contexts aid in defining discrete behavioral regions

Abstract

ABSTRACT Recent research into Caddo bottle and biface morphology yielded evidence for two distinct behavioral regions, across which material culture from Caddo burials expresses significant morphological differences. This study asks whether Perdiz arrow points differ across the same geography, which would extend the pattern of morphological differences to a third category of Caddo material culture. Perdiz arrow points were employed to test the hypothesis that morphological attributes differ, and are predictable, between the two communities. The analysis of linear metrics indicated a significant difference in morphology by behavioral region. Using linear metrics combined with the tools of machine learning, a predictive model – support vector machine – was used to assess the degree to which community differences could be predicted, achieving a receiver operator curve score of 97% and an accuracy score of 94%. The landmark geometric morphometric analysis identified significant differences in Perdiz arrow point shape and size between behavioral regions – one characterized by a comparatively smaller blade and larger stem (north), and the other by a comparatively larger blade and smaller stem (south) – coupled with significant results for modularity and morphological integration. These findings build upon recent investigations that posited two discrete Caddo behavioral regions defined on the basis of discernible morphological differences, expanded here to include a third category of Caddo material culture.