Establishing a limited set of motives characteristic of the human species has been a goal in psychology since the beginning of the discipline. This paper uses a network-based analysis of previously published psychometric data to establish the existence of a pre-defined set of human motives. The set was derived by using evolutionary theory to identify what sorts of goals humans need to achieve to survive and reproduce in the niche our species evolved to fill. The analysis reported here is based on responses obtained from an on-line sample of 510 representative residents of the United Kingdom to 150 items. Analysis shows that all fifteen of the identified motives can be isolated, that they show expected relationships to one another (based on common functionality), and that differences in attentiveness to motives by gender reflect traditional gender-based role-play during human evolution, while differences by age are consistent with expectations from life history theory. The reduced set of 45 items identified by a genetic algorithm-based analysis could form the basis of a psychometric scale. Knowing the set of motives behind goal-directed behaviour should prove a significant boon to a wide variety of psychological applications, including human relations, educational strategies, marketing and behaviour change.