This is the second of two parts on the history of evolutionary theory. Last week, I discussed the gene-eyed view of evolution that came to dominate evolutionary theory of the 20th century. In the 1960s, this view hardened into a dogma, and provoked a reaction, in recognition of the many cooperative networks in nature that are difficult to explain in terms of “kin selection,” the only recourse of the Selfish Gene. In Part Two, below, I continue with the science of multilevel selection (MLS), and talk about why aging is a tough nut to crack. Clearly the selfish gene paradigm is inadequate to explain aging. MLS provides a formal test for deciding whether a given trait can evolve via group selection, and according to these criteria, aging should not be able to evolve.