The change from a solitary life to living in groups is considered one of the major transitions in evolution, and group-living is also a hallmark of the primate radiation. In group-living animals such as primates, decisions that require coordination of activities are not carried out by individuals alone, but are rather negotiated with fellow group members. If there are conflicts of interest among individual group members, however, decisions that require group consensus necessarily implicate a compromise for at least certain individuals in the group. Recent developments in game theory and computer simulation suggest that the level of conflict of interest relative to the benefits of group-living should predict the decision-making mechanism a group displays; i.e. whether a species displays a more democratic or a more despotic mode of reaching a consensus. Empirical studies are still lacking, however, which could refute or provide support for the current theoretical models for the evolution of group decision-making.
The aim of this project by doctoral student Anand Dacier (New York University), under the supervision of Dr. Terry Harrison, is to examine group decision-making in gregarious primates by addressing hypotheses concerning the mechanisms by which groups come to a consensus (despotic vs. democratic); whether conflict of interest among group members can predict group decision-making; how leadership is distributed across the group; and the consequences of decision-making in terms of reproductive success for individual group members. This study employs a novel methodological approach, in which conflict of interest among individuals will be artificially created via manipulating the spatial distribution and temporal availability of resources in feeding platforms. By following this novel experimental setup, the study empirically evaluates the recently developed theoretical models for the evolution of group decision-making, and whether such models are adequate to explain the variation in group decision-making seen across the primate order. By exploring how animal groups come to collective decisions, this study contributes to the broader discussion on the evolution of sociality and the mechanisms that help maintain it.
