A macroevolutionary analysis of European Late Upper Palaeolithic stone tool shape using a Bayesian phylodynamic framework

Phylogenetic models are commonly used in paleobiology to study the patterns and processes of organismal evolution. In the human sciences, phylogenetic methods have been deployed for reconstructing ancestor-descendant relationships using linguistic and material culture data. Within evolutionary archaeology specifically, phylogenetic analyses based on maximum parsimony and discrete traits dominate, which sets limitations for the downstream role cultural phylogenies, once derived, can play in more elaborate analytical pipelines. Moreover, the use of discrete character traits in these efforts prevails, which in turn sets a number of non-trivial challenges. Recent methodological advances in Bayesian phylogenetics, however, now allow us to infer evolutionary dynamics using continuous characters. Capitalizing on these developments, we here present an exploratory analysis of cultural macroevolution of projectile point shape evolution in the European Final Palaeolithic and earliest Mesolithic (~15,000-11,000 BP) using a Bayesian phylodynamic approach and the fossilised birth-death process model. This model-based approach leaps far beyond the application of parsimony, in that it not only produces a tree, but also divergence times, and diversification rates, while incorporating uncertainties. This allows us to compare rates to the pronounced climatic changes that occurred during our timeframe. While common in cultural evolutionary analyses of language, the extension of Bayesian phylodynamic models to archaeology represents a major methodological breakthrough.