Random drift and large shifts in popularity of dog breeds.

A simple model of random copying among individuals, similar to the population genetic model of random drift, can predict the variability in the popularity of cultural variants. Here, we show that random drift also explains a biologically relevant cultural phenomenon--changes in the distributions of popularity of dog breeds in the United States in each of the past 50 years. There are, however, interesting deviations from the model that involve large changes in the popularity of certain breeds. By identifying meaningful departures from our null model, we show how it can serve as a foundation for studying culture change quantitatively, using the tools of population genetics.