| Altruism poses a potential problem for evolutionary theory because altruistic individuals provide benefits to others at a cost to themselves, and this cost implies that such behaviour should not evolve. A number of theories have been proposed to account for the existence of apparently altruistic behaviours in nature. Many altruistic acts are directed towards non-kin and do not appear to be reciprocated by others, leading some researchers to propose that cooperative sentiments must have evolved via group selection. However, Zahavi's theory of costly signaling can help explain the evolution of cooperative sentiments, and there has been a recent increase in theoretical and empirical applications of costly signaling theory. When applied to the study of altruism, this theory predicts that altruism can function as an honest signal of unobservable qualities such as abilities, resources, or cooperative intent, so long as the cost of the altruism is sufficiently high to discourage such behaviour in individuals who do not actually possess such qualities. After reviewing the various theories that could potentially account for the evolution of altruism (Chapter 1), I test some predictions about human cooperation derived from costly signaling theory. In Chapter 2, I show that experimental participants were more cooperative when they had cues that they could benefit from having a good reputation, and that there was apparently some competition to be the most generous group member. Furthermore, I show that people tended to trust group members who are cooperative in other contexts (replicated in Chapter 4). Chapter 3 failed to find evidence that artificially granting high status to people makes them more likely to contribute to public goods or punish free-riders, but there was suggestive evidence that physical proximity to the experimenter affected contributions and punishment. In Chapter 4, I found that people tended to trust others who were willing to incur costs to punish those who free-ride on group cooperation, and that men were more punitive than women. In Chapter 5, I present evidence that women find altruistic men more desirable than neutral men for long-term relationships. Together, these results suggest that humans do treat altruism as a signal of willingness to be cooperative. These findings are discussed with respect to the adaptive design of cooperative sentiments as well as the current debate over group selection. |
