"…the ‘environment’ of a gene consists largely of other genes, each of which is itself being selected for its ability to cooperate with its environment of other genes."

"… Genes are selected, not as ‘good’ in isolation, but as good at working against the background of other genes in the gene pool. A good gene must be compatible with, and complementary to, the other genes with whom it has to share a long succession of bodies."

Richard Dawkins. El gen egoista.