Null Models For Cultural And Social Evolution

Analogies between biological and cultural evolution date back to Darwin, yet the analogies have remained loose. Neutral evolution, known to be important in biology, has been proposed as a null model for cultural change, but has not developed into tests for selection on cultural features. Using inference in timeseries of alternative word forms and grammatical constructions, I demonstrate a cultural analog of natural selection on a background of netural evolution. Social evolution, on the other hand, implies selection in a social environment and therefore cannot be described with a neutral model. I propose a model of pure frequency-dependent selection as a generic null model for social evolution, and use the model to illustrate diverse effects of social selection. I derive a non-linear form of frequency-dependent selection from a mechanistic model of mate choice and show unintuitive consequences for evolutionary dynamics. I infer complex forms of frequency dependent selection—including positive and negative frequency-dependent selection at different frequencies—from data regarding the copying of baby names, the fashions of dog breeds, and the use of rare languages, and discuss the implications for cultural diversity.