The parental investment models of Maynard Smith: a retrospective and prospective view

In his paper ‘Parental investment: a prospective analysis’, Maynard Smith (1977, Animal Behaviour, 25, 1–9) introduced a game-theoretic approach to understanding the evolution of parental behaviour and addressed the broad issue of which sex should provide care for the young. This paper was important in that it introduced the use of game theory to the analysis of parental care. It also stimulated empirical work on care. We identify progress that has been made since the publication of the paper. In particular, although Model 2 of Maynard Smith (1977) has been used in several textbooks to explain the evolution of care, subsequent work has shown that this model is not built on a consistent view of how parental care influences future reproductive success through its effect on the sex ratio. Several models incorporate a consistent account in which opportunities to remate after desertion emerge from the analysis, rather than being specified in advance. More generally, it is not possible to consider parental care in isolation from factors such as paternity, mating preferences and mate choice behaviour. We identify various theoretical and empirical issues in the area of parental care research that we believe deserve further study if our understanding of care decisions is to advance. Taken together, the landmark paper of Maynard Smith (1977) stimulated new theoretical and empirical studies in parental care research and led to new insights into the behavioural interactions between males and females.