Multivariate Selection Theory in Primatology: An Introduction to the Concepts and Literature

With its focus on phenotypes, inheritance, and natural selection, evolutionary quantitative genetics constitutes a bridge between the genetic architecture of traits and evolutionary dynamics. This field has produced a vast theoretical literature with numerous empirical studies supporting the basic theoretical principles of quantitative genetics. At minimum, quantitative genetic studies require data concerning phenotype, fitness, and kin relations for individuals in a population. These data are rarely available to primatologists who study primate populations in the wild. Increasingly, however, evolutionary quantitative genetic studies have been conducted on wild and free-ranging primates, and several long-term studies of wild primates are producing the necessary data to conduct quantitative genetic studies. Our goal in this review is to provide a thorough and (hopefully) gentle introduction to quantitative genetic theory, with particular emphasis on multivariate selection theory. We review the basic steps in deriving a multivariate equation for evolutionary change and we then show how this basic equation can be modified in order to study sexual selection, life history theory, evolutionary constraints, allometry, ecological morphology and social behavior. We also discuss the epistemological role of quantitative genetic models as well as basic concepts such as fitness, selection, and adaptation as they pertain to quantitative genetic studies. Finally, we review some recent quantitative genetic studies of wild and free-ranging primates.