Geometric morphometric analysis for the study of the design and function of the archaeological lithic projectile points of Uruguay

Abstract

In Uruguay, Geometric morphometrics (GM) studies in archeology have been exclusively applied to “Fishtail” projectile points. The variability observed in this morphotype is attributed to the modifications due to diverse events such as resharpening or reworked during the history life. In this work, we aim to expand the recognition of the morphological variability of the archaeological lithic projectile point with stem from Uruguay, advance on the functional aspects of these projectiles, and discuss their link with the weapons systems that were used by the indigenous populations of the region. Through optical magnification and non-parametric statistical analysis, we characterize the allometric variation of n = 84 lithic projectile points. To gain independence from the ontogenetic changes, we selected 36 basic designs and analyzed their morphological variation GM. Based on their weight, we were allowed to assign them to the arrow, dart, and spear categories. The principal components analysis and partial least squares showed that shape changes are associated with the blade-stem relationship, which is proportionality 1:1 and 2:1 in negative values and > 2.5:1 and > 3:1 in the positive values. Arrows and darts share the 1:1 and 2:1 relationship morphospaces of this structure. Darts and spears share the one defined by the ratio > 2,5:1 and, finally, the morphospace defined by the ratio > 3:1 was exclusively integrated for spears. The standardization of proportionalities found in this contribution crosses morphological variability and allows us to discuss the versatility of designs and the complementarity between weapon systems.