 A different approach to characterizing and possibly for identifying and delimiting inheritance systems posits that to count as an inheritance system a system has to have evolved for the purpose of transmitting hereditary information, i.e., to have the “meta-function” of producing heritable phenotypes (Shea 2007). In this respect this approach is reminiscent of the extended replicator approach of Sterelny et al. (1996). Other requirements that have been proposed in the literature are the demand for “unlimited” heredity, i.e., unlimited repertoire of variants the system can store and transmit, needed for sustained or cumulative evolution (see discussion in Godfrey-Smith 2000; Maynard Smith &amp; Szathmáry 1995: 43), and the ability to generate fine-grained response to selection (see Griffiths 2001: 460). Both these requirements regard genetic inheritance as having a privileged role in development and evolution in comparison with epigenetic inheritance processes. Jablonka and Lamb address these concerns with evolvability by noting that multiple instances of limited systems of inheritance may exist within one cell (e.g., multiple self-sustaining metabolic cycles), thus extending the repertoire of hereditary variations, and by emphasizing the effects limited hereditary systems can have on the evolution of genetic variations (see the discussion of genetic assimilation below). Jablonka also argues that the requirement for high fidelity of replication (e.g., Sterelny 2001) is not as necessary for inheritance systems that employ filtering mechanisms that ensure that transmitted variations are typically adaptive (Jablonka 2002). For further discussion of the requirement for evolvability see the discussion of Sterelny’s Hoyle conditions in  section 4.6.