This paper investigates the dynamics of co-evolution of various types of animats. For this purpose, we use a problem we call the Blind Hunger Dilemma. This problem investigates the emergence of collective behavior concerned with shared resource. Our model of co-evolution is inspired by Margulis's idea of parasitism and symbiosis which she applies to the origin of the current eukaryotic cell. Originally, the environment we used has only one type of animat. By the invasion of “bacteria,” animats will develop new sensing functionality. Through many generations, they co-evolve in the environment. Our results shows that animats that contributed to the improvement of mean fitness do not necessarily dominate the population. In this paper, we discuss the reasons within the context of biological study.