On the shape of things: A geometric morphometrics approach to investigate Aurignacian group membership

The manufacture of composite projectile technology requires the production and assemblage of tightly fitted parts designed to fulfill a number of distinct functions. Each part combines a number of techno-functional units, and various processes may be responsible for the shape variability of these units. In order to investigate the relative contribution of each process to the overall variability of a projectile implement, one must identify the point of demarcation between its techno-functional units. In the present paper, the concept of shape modularity is introduced to precisely identify this locus. The application of geometric morphometrics and shape modularity to the study of two Aurignacian osseous projectile point types, i.e., split- and massive-based points, reveals interesting patterns. On both types, the maximum width delimits the distal and proximal techno-functional units of these objects. When focusing on the morphometric variability and the geographic distribution of the implements’ proximal unit, the eight shapes identified for split-based points are found over vast regions of Europe. On the other hand, the two proximal shapes defined for massive-based points show a pattern of local, or regional, aggregation. These proximal shapes were likely considered fit for hafting and hunting by the prehistoric populations who reproduced them, and they are interpreted as a proxy for the socially shared rules of production that guided the manufacture of these tool types. They could therefore be used in future studies that aim to identify group membership amongst the Aurignacian metapopulation and the extent of their interactions.