Introduction

Abstract

How do certain inherited traits like behavioural patterns arise in a population? Why do some behavioural patterns exhibit a certain degree of stability over time whereas others do not? These questions are central in the theory of biological evolution. The concept of evolutionary stability introduced in [Maynard Smith/Price 1973] and [Maynard Smith 1974] provides a framework allowing for a formal analysis of these and related problems. (Forerunners of the idea of evolutionary stability can be found in [Fisher 1930], [Hamilton 1967], and [Stewart 1971].) The prime goal of such a theory is to model evolutionary processes in populations of interacting individuals and to explain why certain states of a given population are — in course of the selection process — stable against perturbations induced by mutations. In particular, an explanation is sought how stable polymorphisms of behaviour can arise in a population, as is observed, e.g., in certain mammal societies.