The Silent Cooperator: An Epigenetic Model for Emergence of Altruistic Traits in Biological Systems

Figure 14

An illustration of the different scenarios for emergence of a cooperative behavior in a world of defectors in the model. The dot density here represents the background fitness (gene X fitness) of a cell.

(a) Case 1: a mutation resulting in an instantly expressed cooperative trait, , gets heavily exploited in a world of defectors and most probably dies out, even if it occurred in a cell with higher gene X fitness than its neighbors

(b) Case 2: a mutation resulting in a silent trait, , and the cell carrying the mutation still acts as a defector, , till time after the mutation. Then, it expresses the cooperative behavior, . Here, the silent gene did not spread, and it will die out once it is expressed, similar to Case 1

(c) Case 3: a mutation resulting in a silent trait, , that happened to be on a cell with higher background fitness (gene X fitness) than its neighbors. The mutation spreads in the system via hitchhiking, and if it gets activated after exceeding a critical cluster size, it stays in the system