  Fagan (2016) argues, to the contrary, that on a “model-based” approach, it’s not clear that these two theories are inconsistent. Indeed, Laplane (2017) has more recently pointed out how the CSC can serve to supplement the evolutionary perspective. The presence and number of cancer stem cells can, it has been suggested, affect the rate and nature of evolutionary change in a population of cancer cells. Essentially, if all cells in a tumor are descended from one or a few cancer stem cells, this restricts population size, and thus suggests that to a large extent cancer progression is driven by drift, rather than selection. Rather than see the two theories as mutually exclusive, in other words, we might see the two as complementary, in the process of integration, or overlapping models.