The samples used in the latest research were taken from two victims of the Justinian plague, buried in a gravesite in a small cemetery in the German town of Aschheim. Scientists believe the victims died in the latter stages of the epidemic when it had reached southern Bavaria.
The skeletal remains yielded important clues and raised more questions.
Researchers now believe the Justinian Y. pestis strain originated in Asia, not in Africa as originally thought. But they could not establish a 'molecular clock' so its evolutionary time-scale remains elusive.
This suggests that earlier epidemics, such as the Plague of Athens (430 BC) and the Antonine Plague (165 -180 AD), could also be separate, independent emergences of related Y. pestis strains into humans.
Our response to modern infectious diseases is a direct outcome of lessons learned from ancestral pandemics, say the researchers.
"This study raises intriguing questions about why a pathogen that was both so successful and so deadly died out," said Edward Holmes, an NHMRC Australia Fellow at the University of Sydney. "One testable possibility is that human populations evolved to become less susceptible,"
Wagner said another possibility is that "changes in the climate became less suitable for the plague bacterium to survive in the wild, or there was a lack of suitable rodent reservoirs."
Paul Keim, a Regents' Professor and the Cowden Endowed Chair of Microbiology at NAU said that "Plague has been circulating through civilization for at least 1500 years and characterizing this ancient genome allows us to understand how diseases arise and then spread from continent to continent - even to locations in Arizona."
|Contact: Eric Dieterle|
Northern Arizona University