An Evolutionary and Ecological Analysis of Human Fertility, Mating Patterns, and Parental Investment

Abstract

This chapter considers the evolutionary biology of human fertility, parental investment, and mating and is designed to provide a broad overview of the topic. It focuses on three themes. The first is the timing of life events, including development, reproduction, and aging. Second is the regulation of reproductive rates and its relationship to parental investment. Sexual dimorphism and its relationship to mating systems together are the third theme. Each of these themes is addressed from two perspectives: first, in a comparative cross-species context, and second, in terms of variation within and among human groups. Our primary goal is to introduce a new ecological framework for understanding variations in each of those domains and then to apply the framework to understanding both the special characteristics of our species in a comparative perspective and variations within and among human groups. A secondary goal is to discuss how evolutionary biology can be integrated with more traditional approaches to human demography and the new research questions such integration would generate. The first section of this chapter presents an introduction to life history theory and current thinking in evolutionary biology with respect to the three themes. Since the fitness consequences of alternative fertility and parental investment regimes depend on ecology and individual condition, both specialization and flexibility in life histories are considered. Building on this foundation, an ecological framework for understanding variation in each of those domains is then introduced. The second section discusses humans in a comparative context, with a particular emphasis on the hunterand gatherer lifestyle because of its relevance to the vast majority of human