The evolution of life history theory: Bibliometric analysis of an interdisciplinary research area

Life history theory developed as a branch of formal evolutionary theory concerned with the fitness consequences of allocating energy to reproduction, growth and self-maintenance across the life course. More recently, researchers have advocated its relevance to many psychological and social-science questions. As a scientific paradigm expands its range, its parts can become conceptually isolated from one another, so that in the end it is no longer held together by a common core of shared ideas. Here, we investigate the life history theory literature using quantitative bibliometric methods based on patterns of citation. We found that the literature up to and including 2010 was relatively coherent: it drew on a shared body of core references, and had only weak cluster divisions running along taxonomic lines. The post-2010 literature is more fragmented: it has more marked cluster boundaries, including boundaries within the literature on humans. Specifically, there are two clusters of human literature based around the idea of a fast-slow continuum of individual differences in behaviour that are bibliometrically isolated from the rest of the literature. We also find some evidence suggesting a relative decline in formal mathematical modelling. We point out that the human fast-slow continuum literature is conceptually closer to the non-human ‘pace of life’ literature than to the non-human literature usually referred to as ‘life history theory’.