  To be sure, there are both analogies and disanalogies between evolution in whole organisms, and the evolving population of cancer cells in a tumor (Germain 2012). However, thinking of cancer as a dynamic, evolutionary process, has great potential for applications in cancer treatment, and perhaps also, in prevention. For instance, some have suggested that we might give young girls drugs or nutritional supplements that remodel the breast in ways akin to pregnancy, as a way to prevent the emergence of breast cancer (Katz, et al. 2015). Others suggest that modeling the evolution of multi-drug resistance may help prevent one of the major causes of cancer mortality. Drugs can be more or less effective in different patients, and lose their effectiveness over time. An evolutionary perspective on cancer may shed light on how drug resistance comes about, in patients with more or less intratumor heterogeneity (Greaves 2000, 2007; Frank &amp; Nowak 2004; Merlo, et al. 2006; Greaves and Maley, 2010). 