The aim of this book is to summarise our current knowledge of evolutionary theory as applied to age-structured populations, i.e. populations whose members are not born into distinct generations, and where fertility and survival are functions of age. Although theoretical treatments of this subject date back to the beginnings of population genetics, its growth has been relatively slow until the last decade or so, when important contributions have been made by workers in several different areas. Population geneticists have subjected many species with age-structured populations to experiments and observations, Drosophila and man being the two best-known examples. A clear understanding of the implications of age structure for such processes as selection and genetic drift is therefore necessary for a proper interpretation of experimental findings. Similarly, animal and plant breeders often wish to make predictions about the effects of artificial selection regimes imposed on age-structured populations. An understanding of the effects of natural selection on life-history phenomena, such as ageing and the timing of reproductive effort, also requires a quantitative theory of the effects of selection in relation to age. For these reasons, a survey of the present sort seems timely.

My policy has been to develop the mathematical treatment in some detail, so that the reader can see for himself the logic behind the results presented. I have deliberately kept the mathematics to an elementary level, so that anybody with a knowledge of basic calculus and matrix algebra should have no difficulty in following the derivations. A knowledge of elementary genetics is assumed.