John Graunt (1620-1674) a London merchant haberdasher, was an amateur scientist, an early Fellow of the Royal Society. He was interested in the impact of epidemics, especially the plague, and how plague caused the numbers of deaths, and the age at death, to vary from one year to another. For over 100 years before his time, parishes had kept records of baptisms and deaths, and what was then understood about causes of death was inscribed in the Bills of Mortality. Graunt collected and analyzed these Bills of Mortality. He demonstrated differences between males and females, between London and rural areas, and the ebb and flow of epidemics of plague. He published his work in Natural and Political Observations ... upon the Bills of Mortality (London, 1662). This was the foundation for the science of vital statistics. John Graunt demonstrated the importance of gathering facts in a systematic manner, to identify, characterize and classify health conditions of public health importance.