 Responding to pressure from DST, the extended replicator approach elaborates the account of non-genetic replicators provided by the replicator framework (Dawkins 1976; Hull 1980) to include non-genetic replicators, while retaining the replicator/interactor distinction which both the holism of DST and the multiple systems view of Jablonka and Lamb reject: Replicators form lineages, while interactors, through which replicators interact with the environment, are ephemeral (see  section 2.2  for discussion). Sterelny et al. (1996) emphasize the distinction between genes as factors having “a distinctive informational role in inheritance” and other reliably present developmental resources. According to them, this distinctive informational role explains why genes, and not just any resource, represent the phenotype and have a special developmental role. They embrace other cases of biological replication if they can be informational in the strong sense their account demands. In a nutshell, the main requirements are that the replicator have the biofunction (i.e., proper function or evolutionarily selected function) of representing the phenotype (or aspects of it) and that it play a causal role in the production of the phenotype. Genes according to this view do not have a unique or privileged role in determining the phenotype; however, they do have a distinctive informational role (see  section 2.4).  Whether other types of replicators exist is an empirical matter, and viewing various biological processes as replication may be scientifically productive according to Sterelny et al. (1996). In more recent work, Griffiths appeals to causal specificity for roughly the same purpose. He frames the debate as being about the extent to which non-genetic inheritance is involved in the precise determination of the phenotype, or how specific the causal relation is (see  section 2.4).