A scientific answer to suicidology’s central question, “Why do people kill themselves?” can take two forms, and they are complementary, not competing. A proximate explanation addresses mechanistic causation—psychological experiences, interactions of risk factors, and suchlike. An ultimate explanation speaks to the behaviour’s evolution in the human species. A coherent understanding of suicide requires integration of the two levels of analysis. However, suicidology has traditionally focussed on the proximate and neglected the ultimate, thereby missing half the explanatory story and hobbling the research effort. This chapter encourages a healthy rebalancing of priorities. The publication of this chapter marks a breakthrough in that it indicates an emerging rapprochement between suicidology and human evolutionary science. The two fields need each other. “Why do people kill themselves?” is a key question for evolutionists too: how could natural selection, powered by the Darwinian “Struggle for Existence”, have produced an animal that wilfully and voluntarily deselects itself from the struggle? Seeking to resolve the paradox are more than a score of evolutionary hypotheses, advanced from diverse disciplines. The chapter outlines, critiques, and organises the various ideas into a conceptual map, intended to mark out the most promising throughways. The hypotheses are set out in five sections reflecting different genres of theory: non-reproductivity theories, kin and group selection theories, pathology theories, communication theories, and escape theories. The authors find the last of these most promising: “escape”-type evolutionary theories broadly align with several existing proximate theories in suicidology, but they raise important new questions for researchers. The primary obstacle to an evolutionary suicidology may be more psychological than technical, because an evolutionary view may require suicide to be understood as a universal feature of our species: there is potentially a suicidal person in us all.