SIGNALING AMONG RELATIVES .1. IS COSTLY SIGNALING TOO COSTLY

Zahavi's handicap principle, originally proposed as an explanation for sexual selection of elaborate male traits, suggests that a sufficient cost to dishonest signals call outweigh the rewards of deception and allow individuals to communicate honestly. Maynard Smith (1991) and Jo hnstone & Grafen (1992) introduce the Sir Philip Sidney game in order to extend the handicap principle to interactions among related individ uals, and to demonstrate that stable costly signalling systems can exi st among relatives. In this paper we demonstrate that despite the bene fits associated with honest information transfer, the costs incurred i n a stable costly signalling system may leave all participants worse o ff than they would be in a system with no signalling at all. In both t he discrete and continuous forms of the Sir Philip Sidney game, there exist conditions under which costly signalling among relatives, while stable, is so costly that it is disadvantageous compared with no signa lling at all. We determine the factors which dictate signal cost and s ignal benefit in a generalized version of this game, and explain how s ignal cost can exceed signal value. Such results raise concerns about the evolutionary pathways which could have led to the existence of sig nalling equilibria in nature. The paper stresses the importance of com paring signalling equilibria with other possible strategies, before dr awing conclusions regarding the optimality of signalling.