Charles Darwin said in On the Origin of Species:competition will generally be most severe between those forms which are most nearly related to each other in habits, constitution and structure.
Richard Dawkins said in The Selfish Gene:As far as a gene is concerned, its alleles are its deadly rivals, but other genes are just a part of its environment, comparable to temperature, food, predators, or companions.This shows the main difference between classical Darwinism and the modern gene-centric view of evolution.
