Post-apocalyptic fiction taps into the deepest springs of ancient and evolved emotions, but it found in modernity a particularly hospitable cultural ecology and a particularly receptive audience. Focusing on post-apocalyptic English language science fiction and horror literature of the Cold War era, I argue that a biocultural analytical framework is indispensable to making sense of this type of fiction. Post-apocalyptic stories function as a mental testing-ground where readers can cognitively and emotionally model the experience of living through the worst, and the genre prompts readers to reflect on the meaning of an existence that is always subject to radical change.