Interest in incorporating life history theory from evolutionary biology into the human sciences has grown rapidly in recent years. Two core features of this research have the potential to prove valuable in strengthening theoretical frameworks in the health and social sciences: the idea that there is a fundamental trade-off between reproduction and health; and that environmental influences are important in determining life history outcomes. There is a barrier to furthering this interdisciplinary agenda, however: the term 'life history theory' is applied to quite different research programmes in the evolutionary human sciences, creating considerable confusion in the literature. Making progress in this field therefore requires that the conceptual differences between these research programmes are recognized. Here, I review the different approaches to studying life history, and related behavioural, outcomes from evolutionary biologists, anthropologists and psychologists, and describe the conceptual and historical differences between them. I then make recommendations for improving the usefulness of this literature, which include: greater precision when using the language of life history theory, greater emphasis on life history trade-offs rather than life history strategies, and more empirical work examining life history outcomes cross-culturally, and investigating how life history and behavioral outcomes may be related. Taming the confusion in the human life history literature is important because a rigorous, theoretically and empirically sound research programme on human life history has the potential to better our understanding of human health and behaviour.