FIGURE 3. Replicator model with diffusion (population-wide averages).

We start from the final state of Fig. 1 and increase diffusion rate step by step. Parameters as in Fig. 1, except diffusion rate: At t = 4,000,000 D = 0.00001 (replication event/movement due to a diffusion ratio of 12.5) and D jumps to 0.0001 (replication event/movement due to diffusion ratio of 1.6); 0.0002 and 0.0003 after every 10⁶ Monte Carlo steps. Plates show the spatial distribution of replicators at t = 4,000,000 and t = 8,000,000 on two spatial scales. Upper plates show the whole arena; lower plates display an enlarged 100 100 part of it. Parasite and altruist replicators are distinguished on the basis of their lengths, according to Fig. 2a b. Parasites (replicators, shorter than 25) are represented in red; altruist replicators (at least 25 monomers) are represented in blue. Empty sites are white.