 In the hierarchy theory of evolution, a distinction is made between two types of hierarchies and the corresponding levels (Eldredge 1996; Vrba &amp; Eldredge 1984): The ecological and the genealogical hierarchy. In both kinds of hierarchies, higher-level things are formed through specific interactions among lower-level things. In the ecological hierarchy, these interactions are exchanges of matter and energy, such as consuming and gathering resources, and in this hierarchy, we find things such as cells, organisms, avatars and ecosystems. In the genealogical hierarchy, the defining activity through which levels are formed is the transmission of information through replication, and the hierarchy includes things such as cells, organisms, demes and species. Note that cells and organisms appear in both hierarchies, but in the ecological hierarchy they are seen as interactors, whereas in the genealogical hierarchy they are seen as replicators.