selfish gene theory
Darwin’s theory of natural selection applied at the genetic level, which proposes that the unit of selection in evolution is not the species or the organism, but the gene.
See also
The Selfish Gene. by Richard Dawkins. Oxford University Press, USA; 2 edition (October 25, 1990). ISBN: 0192860925
The Selfish Gene. by Richard Dawkins. Oxford University Press, USA; 3rd edition (March 31, 2006). ISBN: 0199291152
Genes in Conflict : The Biology of Selfish Genetic Elements (Hardcover). by Austin Burt, Robert Trivers. Belknap Press (January 15, 2006). ISBN: 0674017137