This article examines the parallel histories of medicine and history to about 1450. They emerged together as part of the shift from poetry to prose in Greek culture in the fifth century BC. They each pursued similar strategies of observation, compilation, and analysis. Hippocratic medicine provided a paradigm for Thucydides‟ development of analytic history. Medicine was further systematised by Galen in the second century AD. After the collapse and division of the Roman Empire, the Dar al-Islam became the main area of intellectual advance. Its scholars had little interest in Graeco-Roman historians, but they translated and used the scientific and medical writers. In both history and medicine they tried to create sciences based on Aristotelian philosophy. The article looks in particular at Avicenna‟s attempt to reconcile Aristotle and Galen, and compares this with the eighteenth century debate between preformationists and epigeneticists. It emphasises the need to look at such arguments in the context of their times, and notes the continuing tension between the simplicity of theory and the messiness of data. The transfer of learning from the Dar al-Islam into Western Europe paralleled that from the Graeco-Roman world into the Dar al-Islam. Again, historical writing was overlooked, but philosophical, scientific, and medical writers were translated. They would be the basis for the development of modern science.