Abstract
Demographic models of human cultural evolution have high explanatory potential but weak empirical support. Here we use climate-based estimates of ancient population densities and a global dataset of rock art sites to test an epidemiological model, where the spread of an innovation requires population density beyond a critical threshold. The model has stronger empirical support than a null model where rock art distribution and population density are independent. Tests for different areas and periods, and with independent population estimates, yield qualitatively similar results, supporting the robustness of the model. We conclude that a minimum population density is a necessary condition for the spread of rock art. Similar methods could be used to test the model for other artefacts and to compare it against other models.
One Sentence Summary Combining climate-based estimates of ancient population densities with data for the global distribution of rock art over the last 46,000 years, we provide robust evidence that the diffusion of rock art requires population densities above a critical threshold.