An analysis of the teeth of people from Bronze Age Europe and Asia has shown that the plague or more formally the bacterium that causes the disease, Yersinia pestis, evolved to be a massive killer at least 3,500 years earlier than previously thought. Eske Willerslev of the Center for GeoGenetics at the University of Copenhagen examined the teeth of people across the globe in an effort to determine when the bacterium became virulent and acquired fleas as a vector.
Teeth retain the integrity of DNA longer than any other human tissue and can be used to track the progression of disease. The researchers examined the teeth of seven individuals collected from museums and archaeological excavations. The teeth were dated between 2,794 B. C. E. and 951 B. C. E. An analysis of the most common ancestor of Yersinia pestis showed that the bacterium was virulent and transmissible to fleas 5,783 years ago. The bacterium adapted to human host by losing its flagellum because an antibody in humans targets one protein in flagella.
One simple alteration in the flea genome enabled the bacterium to use fleas as a host and infect people with the plague. The discovery is considered proof that the Plague of Athens that occurred 2,500 years ago and the Antonine Plague that devastated the Roman Army 1,700 years ago were the plague. The researchers contend that the plague may have been with man since prehistoric times. A change in plague DNA and flea DNA that occurred close to the same point in time produced the prolific killer that is still with us today