Crossing the Threshold: The Role of Demographic Stochasticity in the Evolution of Cooperation (Tom LoFaro, Gustavus Adolphus College)

When Charles Darwin began writing “On the Origin of Species” he knew that explaining cooperative behavior in the context of “survival of the fittest” was problematic.  In fact, this apparent contradiction puzzled ecologists for many years after.  In this talk we will discuss a mathematical model of the evolution of cooperation developed by Doebeli, Blarer, and Ackermann that incorporates ideas from game theory into a standard population genetics model.  We will show that if the model is viewed deterministically then cooperative behavior cannot spread from rarity.  However, if birth rates are stochastic then cooperative behavior might spread.  We will explore why this is so and describe conditions that increase the probability that cooperative behavior will become established.