Parental-Offspring Conflict

Disputes between parents and their young might seem easy enough to spot in everyday human life, but the notion of a general, evolutionary conflict between offspring and their parents has proved surprisingly slippery (reviewed by Godfray 1995). Nevertheless, today, almost four decades since the concept was first proposed by Trivers (1974), parent-offspring conflict has theoretically robust foundations (reviewed by Godfray 1995; Godfray and Johnstone 2000) and there is diverse evidence that it is a significant selective force in nature (although perhaps not always in the ways initially assumed, reviewed by Kilner and Hinde 2008). In a recent review, we showed how information warfare lies at the heart of parent-offspring conflict in many instances. Readers specifically interested in signalling by young animals and their parents, as well as other uses of personal information, may wish to consult Kilner and Hinde 2008 before ploughing ahead here. Our aim in this chapter is to attempt to reconstruct the evolutionary consequences of this conflict for traits in offspring and their parents, focusing relatively little on signalling this time. We start with a quick recap of basic conflict theory before outlining diverse empirical evidence for an evolutionary conflict between parents and their young. Next we consider how conflict might link pairs of traits in parents and their offspring, showing how co-evolution between the two parties becomes focused on these particular characters. We conclude with a discussion about the outcomes of parent-offspring conflict: does it always end in a stable equilibrium between parents and their young, as predicted by the many ‘resolution’ models of conflict? Or is instability widespread, with parents and offspring frequently alternating in who gains the upperhand?