The Influences of Life Stages on the Evolution of Altruism
by
Caitlin Ross
University of North Carolina at Greensboro
Coauthors: Kayla Jackson, Dr. Jan Rychtar, Dr. Olav Rueppell

The evolution of altruistic behavior is intriguing because selfish actions often seem to benefit the individual. Game theorists often model this predicament by using the Prisoner’s Dilemma. Two players simultaneously decide on a strategy, and though a defector whose partner cooperates will benefit most, mutual defection yields the worst consequences for both players. When using this game to study the evolution of cooperation, it has been shown that spatial structure favors altruistic behavior. Based on the model of Szolnoki et al. (2009), we study how life stages affect the evolution of cooperation in a spatially structured, aging population. The spatial structure of the model allows for the evolution of cooperation in otherwise inherently selfish populations. We examine how changing the existence and length of pre-reproductive, reproductive, and post-reproductive stages of life affects the evolution of altruism. Using computer simulation, we show that in general, a proportionally long reproductive stage allows cooperators to thrive best. The existence of any non-reproductive stage suppresses cooperation—post-reproductive more substantially than pre-reproductive. Therefore, our study suggests that cooperation evolves most likely in populations with simple life history, at least when interactions between different life stages are symmetrical.

Date received: June 29, 2012