Classic theories for the evolution of senescence predict that rates of aging should be highest in populations in which extrinsic mortality is high. This predication is called into question in new work by David Reznick and co-workers, who found that guppies Poecilia reticulata derived from natural populations with high levels of predation live the longest in the laboratory. This study illustrates that the effect of mortality on aging might depend on how we define aging, and on the particular cause of increased mortality.