Our Children: Parental Decisions — How Much to Invest in Your Offspring

Reproduction is the most fundamental of evolutionary behaviors, yet human parents face especially complex tradeoffs when deciding how many children to have and how much to invest in each of them. This chapter reviews parental investment theory, including both the key concepts and some important questions to which they have been applied in humans. Written primarily from the perspective of human behavioral ecology, this chapter also discusses how evolutionary social scientists have approached cross-cultural variation in parenting behavior. The chapter begins with an overview of life history theory and the concept of reproductive tradeoffs, focusing especially on the tradeoffs between current vs. future reproduction and quantity vs. quality of offspring. Discussing the critical question of who invests in offspring, I next compare motivations for investment between mothers and fathers, and explore the roles of many types of kin in investment, while considering whether humans can be viewed as cooperative breeders. I then explore the role of parent–offspring conflict and sibling conflict in parental investment and inheritance systems, followed by an exploration of sex biases in investment, including the Trivers–Willard effect local resource competition, and local resource enhancement. In conclusion, I argue that parental investment has been one of the most active areas of enquiry among evolutionary researchers over the last twenty years, and is likely to remain one of the mainstays of the field during the coming decades.