What role does speaker population size play in shaping rates of language evolution? There has been little consensus on the expected relationship between rates and patterns of language change and speaker population size, with some predicting faster rates of change in smaller populations, and others expecting greater change in larger populations. The growth of comparative databases has allowed population size effects to be investigated across a wide range of language groups, with mixed results. One recent study of a group of Polynesian languages revealed greater rates of word gain in larger populations and greater rates of word loss in smaller populations. However, that test was restricted to 20 closely related languages from small Oceanic islands. Here, we test if this pattern is a general feature of language evolution across a larger and more diverse sample of languages from both continental and island populations. We analyzed comparative language data for 153 pairs of closely-related sister languages from three of the world's largest language families: Austronesian, Indo-European, and Niger-Congo. We find some evidence that rates of word loss are significantly greater in smaller languages for the Indo-European comparisons, but we find no significant patterns in the other two language families. These results suggest either that the influence of population size on rates and patterns of language evolution is not universal, or that it is sufficiently weak that it may be overwhelmed by other influences in some cases. Further investigation, for a greater number of language comparisons and a wider range of language features, may determine which of these explanations holds true.

Languages change over time, and the evolution of languages is similar in many ways to biological evolution. But are all patterns predicted by evolutionary theory also seen in language evolution? One well-known biological pattern is that smaller populations tend to lose genetic diversity, and large populations tend to become more genetically diverse, but the effect of population size on language evolution is highly debated. Do small populations have faster rates of change through greater diffusion of new words, or slower rates of change due to strict language transmission? Do large populations gain words faster through more innovators, or lose faster due to simplification across varied speaker communities? This extract, taken from Welsh's (2015) Honours thesis, provides the background on the relationship between population size and rate of language change, discusses some of the contrasting hypotheses and methodological techniques and explains the research currently being conducted that attempts to clarify the relationship.