The distinction between the historical and theoretical sciences runs through rather than between academic disciplines. Some branches of biology, like evolutionary biology, genetics, and phylogeny, are historical. Other branches that study types of biological objects in theoretical contexts independent of space and time, like biochemistry, anatomy, and cell biology, are theoretical. The historical sciences infer origins, common causes of information-preserving effects in the present: phylogeny and evolutionary biology infer the origins of species from homologies, genome sequences, and fossils. Historians of humanity infer past events and processes from their effects in the present, documents, material remains, visual depictions, and recordings. I explicate the ontological distinction between types and tokens that lies at the basis of the distinction between the historical and theoretical sciences. Then, I demonstrate how this distinction leads to different epistemic methodologies for the historical and theoretical sciences. Finally, I address the heuristic issue of explanation in the historical and theoretical sciences. I distinguish two senses of explanation in the historical sciences: a strict one that explains the evidence and looser and context-dependent one that explains representations of historical events. Explanations in the second sense, that is, explanations of events, explain the evidence in the first sense. The evidence and events that the historical sciences explain are tokens. The theoretical sciences, by contrast, are not interested in token evidence and events, but in types of replicated evidence and repeated events.