For example, a pond is dark in color. There are two alleles. The dark color allele is dominant over the light color one. Let's assume that the relative fitness of both the homozygous dominant and heterozygous is 1, and the relative fitness of the homozygous recessive is 0.5. When I ran the simulation, I changed no other values. My data after 251 generations is this: My question is that being homozygous recessive is clearly less favorable, and even though being homozygous dominant and heterozygous carry the same advantage instead of heterozygote advantage, why wouldn't the recessive allele disappear?