Long-term cultural stability in hunter-gatherers: a case study using traditional and geometric morphometric analysis of lithic stemmed bifacial points from Southern Brazil

Irrespective of the great number of archaeological sites from Southern Brazil presenting bifacial stemmed points, not many detailed studies on their morphological evolution have been carried out so far. We present an extensive study of the morphology of stemmed bifacial projectile points excavated from Garivaldino Rodrigues rockshelter (RS-TQ-58), Rio Grande do Sul, Southern Brazil. Garivaldino presents a range of dates from 11,660 to 7540 cal BP. Multivariate statistics applied to both traditional and geometric morphometric analyses failed to reveal any important changes in shape through time. However, the coefficients of variation presented a significant increase through time in three measurements related to projectile point neck and stem. The absence of change in shape might be related to small group size and low level of cultural innovation. Such cultural stability might be related to novelty-avoiding mechanisms or the operation of a meta-tradition that would be selected in very stable environments. On the other hand, the increase in the variation of linear measurements through time might suggest an increase in population size and copying errors.