Copying error, evolution, and phylogenetic signal in artifactual traditions: An experimental approach using model artifacts

Spatio-temporal patterns of artifactual variation are increasingly being studied via the explicit application of cultural evolutionary theory and methods. Such broad-scale (macroevolutionary) patterns are mediated, however, by a series of small-scale (microevolutionary) processes that occur at the level of individual artifacts, and individual artifact users and producers. Within experimental biology, “model organisms” have played a crucial role in understanding the role of fundamental microevolutionary processes, such as mutation and the inheritance of variation, in respect to macroevolutionary patterns. There has, however, been little equivalent laboratory work to better understand how microevolutionary processes influence macroevolutionary patterns in artifacts and their analysis. Here, we adopt a “model artifact” approach to experimentally study the issues of copy error (mutation) and resultant phylogenetic signal in artifact traditions. We used morphometric procedures to examine shape copying error rates in our “model artifacts.” We first established experimentally that statistically different rates of copying error (mutation) could be induced when participants used two different types of shaping tool to produce copies of foam “artifacts.” Using this as a baseline, we then tested whether these differing mutation rates led to differing phylogenetic signal and accuracy in two separate experimental transmission chains (lineages), involving participants copying the previous participant’s artifact. The analysis demonstrated that phylogenetic reconstruction is more accurate in artifactual lineages where copying error is demonstrably lower. Such results demonstrate how fidelity of transmission impacts directly on the evolution of technological traditions and their empirical analysis. In particular, these results highlight that differing contexts of cultural transmission relating to fidelity might lead to differing patterns of resolution within reconstructed evolutionary sequences. Overall, these analyses demonstrate the importance of a “model artifact” approach in discussions of cultural evolution, equivalent in importance to the use of model organisms in evolutionary biology in order to better understand fundamental microevolutionary processes of direct relevance to macroevolutionary archaeological patterns.