 Evolutionary transitions create new potential levels and units of selection by creating new kinds of entities that can have variances in fitness. Thus, it is the “project of a theory of evolutionary transition to explain the evolutionary origin of entities with such capacities” (Griesemer 2000c: 70). However, since such cases involve the evolutionary origin of a given level of selection, traditional synchronic approaches to units and levels of selection, which assume the pre-existence of a “hierarchy of entities that are potential candidates for units of selection”, may be insufficient, since it is the evolution of those very properties that allow entities to serve as, for example, interactors or replicators that is being addressed (Griesemer 2000c: 70). Such a task requires a diachronic perspective, one under which the properties of our currently extant units of selection cannot be presupposed. 