  Dobzhansky (1973) wrote that “nothing in biology makes sense except in light of evolution.” Can evolutionary thinking shed light on cancer? After all, cancer is ordinarily understood to be a case of failure of otherwise functional controls on cell birth and death. At first pass, this view seems fundamentally at odds with taking an evolutionary perspective on cancer. For, how can something that is an exemplary case of “dysfunction” count as an evolutionary process or product of adaptive evolution? Moreover, how ought we to square this picture of cancer with the fact that cancer cells seem to co-opt developmental processes—i.e., the process of “de-differentiation” typical of early embryonic cells? Is cancer a byproduct of development? Finally, cancer seems to increase in incidence as we age. Is cancer simply a byproduct of aging?  Relatedly, if—as some argue—aging itself is selected for (a contested question!), is cancer in some sense “adaptive”? All these perspectives on cancer require us to perhaps rethink the nature of function and dysfunction, or at least better understand how there are trade-offs in fitness at different temporal and spatial scales over the course of our life and evolutionary history. The best perspective to take on this may be a “multilevel” evolutionary perspective—i.e., thinking of evolution by natural selection as operating at different temporal and spatial scales, both sequentially, and in some cases, simultaneously, sometimes yielding unfortunate “cross-level byproducts” of selection at one temporal and spatial scale, for entities or processes at other temporal or spatial scales (cf. Okasha 2007).