Reconstructing the Past: Scientific Reasoning in the Historical Sciences Through the Lens of Endosymbiotic Theory

Scientific inquiry is often taught through the lens of experimental science, which can obscure how scientists construct knowledge in fields that investigate the past. This paper examines historical scientific reasoning using the development of endosymbiotic theory—the idea that mitochondria and chloroplasts originated from symbiotic bacteria—as a case study. Drawing from philosophy of science and science education literature, I analyze how reasoning strategies such as retrodiction, abductive reasoning, consilience of evidence, and model-based inference enable scientists to construct robust explanations of past events. I also highlight additional reasoning strategies common in historical science, including analogical reasoning, narrative construction, and the method of multiple working hypotheses, and show how they contribute to the development and evaluation of historical explanations. By tracing the evolution of endosymbiotic theory and aligning these reasoning strategies with NGSS scientific practices, I argue for a broader conception of scientific reasoning in classrooms. The paper concludes by demonstrating how integrating historical reasoning into instruction not only supports student understanding of science but also broadens conceptions of scientific inquiry and strengthens scientific literacy.