 The revised definition of replicator corresponds more closely than the original one to a long-standing debate in genetics about how large or small a fragment of a genome ought to count as a replicating unit—something that is copied, and which can be treated separately in evolutionary theory (see especially Lewontin 1970; Hull 1980). This debate revolves critically around the issue of linkage disequilibrium and led some biologists to advocate the usage of parameters referring to the entire genome rather than to allele and genotypic frequencies in genetical models (Lewontin  1974).[5]  The basic point is that with much linkage disequilibrium, individual genes cannot be considered as replicators because they do not behave as separate units during reproduction. Although this debate remains pertinent to the choice of state space of genetical model, it has been eclipsed by concerns about interactors in evolutionary genetics.