Scientists’ use of diagrams in developing mechanistic explanations: A case study from chronobiology

We explore the crucial role of diagrams in scientific reasoning, especially reasoning directed at developing mechanistic explanations of biological phenomena. We offer a case study focusing on one research project that resulted in a published paper advancing a new understanding of the mechanism by which the central circadian oscillator in Synechococcus elongatus controls gene expression. By examining how the diagrams prepared for the paper developed over the course of multiple drafts, we show how the process of generating a new explanation vitally involved the development and integration of multiple versions of different types of diagrams, and how reasoning about the mechanism proceeded in tandem with the development of the diagrams used to represent it.