Abstract:

The geographical distribution of languages evolves driven by human contact, demic diffusion, invasion, etc. The spatial pattern of languages in South America has undergone a substantial change since the European colonization, where the Indo-European (IE) languages extensively expanded their area over the continent, removing many indigenous languages. Our study aims to statistically infer the evolutionary history of the geographical distribution of the IE and indigenous languages after the Age of Discovery, based on known entry locations of IE languages and the modern geographical distribution. We extend the Bayesian framework which interpolates the history of a diffusion process in a spatial network based on incomplete data (Takahashi et al. 2023). We define a spatial network representing the topography of South America. The transition (or diffusion) rates of languages between neighbors are defined considering the hiking distance, which is inferred from elevation data of the terrain. The method reveals the spread of IE languages in South America, indicating the probability of each location being occupied by an IE language at any given point in time. We offer a principled framework for tracing diffusion processes in cultural evolution. The framework incorporates geographical factors, particularly elevation, and examines their influence on diffusion.

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