Selfish DNA

Selfish DNA refers to those sequences of DNA which, in their purest form, have two distinct properties: (1) the DNA sequence spreads by forming additional copies of itself within the genome; and (2) it makes no specific contribution to the reproductive success of its host organism. This idea was sketched briefly by Richard Dawkins in his 1976 book The Selfish Gene and was explicitly exposed in two 1980 articles in Nature magazine. According to one of these articles:

The theory of natural selection, in its more general formulation, deals with the competition between replicating entities. It shows that, in such a competition, the more efficient replicators increase in number at the expense of their less efficient competitors. After a sufficient time, only the most efficient replicators survive.