The pressures that led to the evolution of episodic memory have recently seen much discussion, but a fully satisfactory account of them is still lacking. We seek to make progress in this debate by taking a step backward, identifying four possible ways that episodic memory could evolve in relation to simulationist future planning—a similar and seemingly related ability. After distinguishing each of these possibilities, the paper critically discusses existing accounts of the evolution of episodic memory. It then presents a novel (...) argument in favor of the view that episodic memory is a by-product of the evolution of simulationist future planning. The paper ends by showing that this position allows for the maintenance of the traditional view that episodic memory operates on stored memory traces, as well as explaining a number of key features of episodic memory: its being subject to frequent and systematic errors, its neural co-location with the capacity for simulationist future planning, and the potential existence of non-human episodic memory. (shrink)