In generalized theory of evolution (GE theory), the three core principles of In the − reproduction, variation and selection − are detached from the level of biological evolution (BE), abstracted and extended to other domains, in particular to the domain of cultural evolution (CE). In this talk I investigate the ontological foundations of GE and CE theory. They consist in entities and structures that must be realized to get the three modules of evolution running. These entities include self-reproducing systems with variation and populations of such systems in environments with limited resources. A major difference between the reproductive units of BE and CE consists in the fact that genes act as constructors of evolutionary systems, while memes play the role of modificators. The abductive justification of GE and CE theory that proceeds in three step: First, CE theory is justified, second, based on the first step GE theory is abductively justified as the common core of BE and GE, and thirdly, the fruitfulness of GE theory is demonstrated by its applicability to further domains.