This chapter presents the results of an in-depth study of fertility and parental investment among a representative sample of men from Albuquerque, New Mexico. It aims to develop and test a general theory of human fertility and parental investment, with a specific focus on explaining recent historical trends in family behaviour within developed nations. The chapter provides a theoretical framework that unifies life history theory, developed in biology, with human capital and household allocation theories, developed in economics. It offers a specific theory of modern fertility reduction based upon the emergence of skills-based competitive labour markets. Understanding the role of status competition during human evolutionary history may prove particularly illuminating in explaining the pattern of high consumption and low fertility. From an evolutionary perspective, it is necessary to specify the critical differences between pre- and post-demographic transition societies and to show why the suite of proximate mechanisms that evolved to regulate fertility.