This chapter presents a new formulation which not only covers the fully non-cooperative behavior and the fully cooperative behavior, but also the fully altruistic behaviour. To do so, we make use of the evolutionary game theory which we extend to cover this kind of behavior. The major focus of this work is to study how the level of cooperation impacts the profile of population as well as the global performance of the system. equilibrium of the system through the notion of Evolutionary Stable Strategies and study the effect of transmission cost and cooperation level. We define and characterize the equilibrium (called Evolutionary Stable Strategy) for these games and establish the optimal level of cooperation that maximizes the probability of successful transmission. Our theoretical results unveil some behaviors. More specifically, we show that when all users increase their level of cooperation, then the performance of the system is not necessary improved. In fact, for some scenarios, the performance of groups may lead to an improvement by adopting selfishness instead of altruism. This happened when the density of agents is high. For low density, the degree of cooperation may indeed improve the performance of all groups. According to the structure of the ESS, we try to evaluate the performance of the global system in order to derive the optimal degree of cooperation. In this chapter, we explore our finding to study multiple access games with a large population of mobiles decomposed into several groups. Mobiles interfere with each others through many local interactions. We assume that each mobile 25