Plague infection in humans began in Bronze Age

London: Plague has been endemic in the human population since the beginning of the Bronze Age, more than 5,000 years ago, new research has found.

The findings based on analysis of ancient DNA suggest that plague was endemic in the human populations of Eurasia at least 3,000 years before the first plague pandemic in historical records -- the Plague of Justinian in 541 AD.

The researchers also found that the ancestral plague would have been predominantly spread by human-to-human contact -- until genetic mutations allowed Yersinia pestis (Y. pestis), the bacteria that causes plague, to survive in the gut of fleas.

These mutations, which may have occurred near the turn of the first millennium BC, gave rise to the bubonic form of plague that spreads at terrifying speed through flea -- and consequently rat -

carriers, the study said.

The bubonic plague caused the pandemics that decimated global populations, including the Black Death, which wiped out half the population of Europe in the 14th century.