A geometric morphometrics-based assessment of blade shape differences among Paleoindian projectile point types from western North America

Blade shape features in the type definitions of Clovis, Folsom, and Plainview projectile points. However, the accuracy of these assessments has never been evaluated. Here we report a study in which geometric morphometrics and multivariate statistics were used to compare the shapes of the blades of Clovis, Folsom and Plainview points from the Southern Plains of North America. In the course of the analyses, we controlled for the impact of three potential confounding factors: allometry, differences in raw material quality, and resharpening. The analyses show that blade shape distinguishes Clovis points from both Folsom points and Plainview points, but does not distinguish Folsom points from Plainview points. The analyses also show that the similarities and differences in blade shape among the types are independent of allometry, raw material quality, and resharpening. These findings suggest that the type definitions for Clovis, Folsom and Plainview need to be altered. They also have implications for typing specimens that lack other defining characters (e.g. channel flakes, flutes). Lastly, the absence of resharpening effects raises questions about the validity of the reduction thesis.