Experimental assessment of lanceolate projectile point and haft robustness

Abstract

Stone lanceolate projectile points are characterized as having a lance shape with a tip tapering to an apex and are found in the archaeological record at different times and places across the world. In North America, lanceolate points are an important component of the Paleoindian period. One of the main factors in the design of lanceolate points is robusticity, which refers to how much of a point breaks as a result of failure of the stone upon impact. In this paper we investigate the factors that influence the robustness of lanceolate projectile points. To do this, we present results of a controlled ballistic experiment using 412 projectile points of 14 different lanceolate forms to investigate differences in point robustness. We hafted these points to darts and fired them into an oak board to induce impact failure. We then analyzed the resulting point breakage and haft damage. To assess the influence of point characteristics on point breakage we constructed a Bayesian zero-inflated negative binomial regression model. Results show short, wide, and thick blade forms were more robust than long, narrow, and thin blades. Using a separate Bayesian binomial model, we also found that haft damage occurred more often with the more robust points. Therefore, we suggest that a trade-off between point and haft robustness was likely an important consideration for prehistoric flintknappers when designing their weapons.