THE HANDICAP PRINCIPLE IN PARENT-OFFSPRING CONFLICT - COMPARISON OF OPTIMALITY AND POPULATION GENETIC ANALYSES

The evolution of offspring handicap is studied in two ways. First, the problem is formulated in terms of a population game in which each player, parent and offspring, seeks to increase its own fitness. Second, we study the dynamics of an exact two-locus model in which one locus affects the behavior of offspring and the other affects that of parents. It is shown that the latter approach leads to a more complicated "game structure," in which parents maximize a weighted average number of offspring, with lower weight ascribed to the handicapped type. The weights depend on the rate of recombination. Under the assumption of fitness maximization, used in the game-theoretical approach, it is shown that a handicap always evolves. The two-locus analysis, however, produces a more realistic set of specific conditions for initial success and fixation of the handicap. When linkage is loose, these latter conditions coincide with a verbal prediction of Zahavi. With tight linkage, however, conditions for this evolution of offspring handicap are significantly restricted.