How can we confirm, from a microbiological perspective, descriptions of ancient diseases known until today only on historical, archeological, and anthropological bases? Can we access ancient pathogens, and is it possible to reconstruct their history and evolution? Researchers from the Rickettsies Unit (CNRS - University of the Mediterranean) and the Human Adaptability Laboratory : biology and culture (CNRS - University of the Mediterranean) in Marseille, France have put forward the hypothesis that dental pulp could serve as a remarkably well preserved material for studying the ancient infectious agents responsible for septicemia. They applied techniques from molecular biology to amplify genes and sequence nucleic acids extracted from samples of dental pulp from 16th and 17th century mass graves, identified as coinciding with the epidemics of plague that ravaged that period. This method allowed them to make the first successful paleomicrobiological diagnosis of an ancient septicemia illness. The results obtained, when compared with witness samples from the same period, confirm that the mass graves do indeed indicate plague epidemics. They also show that bubonic plague was a morbid entity clearly identified by doctors from the end of the 16th century. This work, combining researchers from the Humanities and the Life Sciences at the center of a new scientific discipline, paleomicrobiology, open the way for methodical exploration of ancient septicemial epidemics, such as the medieval Black Plague or typhus.