Intentional cranial modifications in the Americas: The temporal and spatial patterns of potential transmissions and cultural innovations

For at least 10,000 years, people from many cultures have demonstrated social status or group affiliation by performing intentional cranial modification (ICM), altering head shape for life in early infancy. We present a database of ICM cases (n = 1,772) across the Americas, where this practice was prominent and widespread, and use spatial statistics to explore spatiotemporal variations in the prevalence of ICM in this region from a cultural evolutionary perspective. Prediction surfaces produced using Empirical Bayesian Kriging suggested that ICM first occurred in Central America. The spatial extent of this practice then broadened to encompass North and South Americas. Spatial analyses suggest that annular ICM cases appeared where tabular cases were present and its geographic range increased rapidly relative to tabular ICM. This suggests that annular ICM may be a derived cultural behavior and that existing familiarity with cranial modification behaviors aided the adoption of additional methods of head shaping.