The Evolution of Imitation Without Cultural Transmission

Abstract

The evolution and function of imitation in animal learning has always been associated with its crucial role in cultural transmission and evolution. Can imitation evolve in the absence of cultural transmission? We investigate a model of a semelparous organism with discrete, nonoverlapping generations in which the sole transmission of information between generations is genetic. We suppose that an organism can modify its phenotype in response to the phenotypes it observes in its cohort of conspecifics. We find that during a period of directional selection towards a phenotypic optimum, natural selection favors modifiers which cause an organism to bias its plastic phenotype in the direction \emph{opposite} to the mean phenotype of the population. As the population approaches the phenotypic optimum and shifts into stabilizing selection, selection on the modifier reverses and favors strong imitation of the population mean. Imitation can become so strong that ``genotype-phenotype disengagement'' occurs (Gonzalez, Watson, and Bullock 2017), and for multivariate phenotypes evolution can cycle between genotype disengagement and re-engagement. While in some cases the evolution of imitation and anti-imitation increase the mean fitness of the population, cycles of genotype disengagement and re-engagement can make the mean fitness nonmonotonic in time.