 The increasing focus by biologists on DNA as a “master molecule” containing coded genetic information, after the discovery of the double helix structure in 1953, on the one hand, and the gene-selectionist view articulated in 1966 by George Williams in his book Adaptation and Natural Selection, which culminated in the “replicator” concept in philosophy of biology (Dawkins 1976; Hull 1980, see entry:  Replication and Reproduction),  on the other, led to a tendency to view biological inheritance as consisting of a single channel of transmission. This channel is understood to involve the inheritance of genetic information encoded in DNA (or, in some viruses in RNA), a view often referred to as “geno-centrism”. It should be noted that the replicator concept itself does not rule out non-genetic replicators (Dawkins 1976, see also the discussion by Sterelny, Smith, &amp; Dickison 1996). The dual-inheritance model of biological and cultural evolution which is based on two types of replicators, genes and memes, is a paradigmatic example that is based on the replicator framework, and that involves both more than one channel of inheritance and non-genetic inheritance (for detailed discussion of the notion of cultural inheritance see the entry on  cultural evolution).  Accounts of heredity that are based on the notion of replicators may approach non-genetic inheritance by characterizing multiple kinds of replicators (e.g., memes), each of which is supposed to underlie a different channel of non-genetic inheritance. John Maynard Smith and Eörs Szathmáry’s account of Major Transitions in Evolution is organized around transitions to new kinds of ways in which information is stored and transmitted, understood as transitions to new kinds of replicating entities (Maynard Smith &amp; Szathmáry 1995), and multiple types of replicators are embraced by the notion of the extended replicator (Sterelny 2001; Sterelny et al. 1996, see entry:  Replication and Reproduction)  discussed below. More typically, however, non-genetic forms of inheritance, with the possible exception of cultural inheritance in a few groups of higher animals, are often ruled out as not fulfilling the requirements imposed by the definition of a replicator (regarding the debate whether human cultural evolution is best understood through applying a replicator framework to learning and imitation, see Lewens 2015, chps. 1 and 2). It should be emphasized that the replicator view posited replicators, typically genes, as the unit of selection; the work discussed in this entry is concerned with the biological processes and mechanisms involved in inheritance, and is not concerned directly with the debate about the unit of selection. Implications regarding selection are elaborated in  section 4.1.