The cultural transmission of acquired variation: effects on genetic fitness.

In a cultural species individuals acquire some aspects of their phenotypes by imitating conspecifics. Presumably, cultural transmission has some adaptive function in such species. Some authors have suggested that one such function may be the ability to transmit phenotypes that have been modified by learning or some other form of phenotypic plasticity. To examine this hypothesis we have compared the genetic fitness of cultural and noncultural individuals in three different models. In each model the environment is assumed to be variable, either in space or time, and learning modifies each individual's phenotype so as to increase the individual's fitness in the local environment. Cultural individuals transmit the modified phenotype to their offspring, while noncultural individuals do not. The models are different in the following ways: two models assume a dichotomous phenotype, one in a temporally varying environment and one in a spatially varying environment; the third model assumes a quantitative phenotype in a temporally variable environment. The two models which assume a temporally varying environment yield similar results. Genetic transmission is favored in highly autocorrelated environments while cultural transmission in environments with intermediate autocorrelation. In the spatially varying model cultural transmission is always favored.