Theoretical aspects of the mode of transmission in cultural inheritance

This study investigates how evolutionary factors interact to determine the relative importance of vertical versus nonvertical mode of transmission in cultural inheritance. Simple mathematical models are provided to study the joint evolution of two cultural characters, one determining the viability a nd the fertility of individuals, and the other determining the vertical tra nsmission rate of the first trait. Ordinary local stability analyses indica te that intrademic processes should lead to a greater reliance on vertical cultural transmission. On the other hand, when newly arisen variants are ad aptive and favored in biased cultural transmission, interdemic processes ma y lead to a decrease in vertical transmission. This is because biased nonve rtical transmission may effectively propagate the adaptive variants, furthe r increasing the average growth rate of the population. These results are v erified under several distinct sets of assumptions. It is also inferred tha t the degree and intensity of transmission bias may be the important determ inants of cultural processes. (C) 1999 Academic Press.