Population size and linguistic evolution

The impact of demography on cultural evolution has been investigated in modelling and simulation work, but few studies have explored this relationship with empirical data. Importantly, no pertinent studies have controlled for the historical non-independence of evolutionarily related languages (Galton's Problem). Here we test the relationship between linguistic change and population size / density using data from 351 Austronesian languages. To quantify language evolution, we use phylogenetic methods to estimate lexical replacement (word turnover) in core vocabulary. Controlling for historical splitting events, we use these estimates of the rates of linguistic evolution and find (a) strong phylogenetic signal in population size and density, (b) a significant but weak relationship between lexical replacement and population size, but not density, and (c) a strong effect of splitting events on both size and density. We discuss these results relative to the Austronesian expansion and more general implications for language-culture coevolution