It's never too late to be exonerated and black rats couldn't agree more.
After centuries of taking the blame for the bubonic plague in Europe, it has been found the despised black rats didn't cause the epidemic and the most likely culprits were cute little gerbils, shows a new study.
In the study - published in the Proceedings of the National Academy of Sciences - scientists from the University of Oslo in Norway tracked climate data from the 14th century and opined that rats possibly couldn't have caused the epidemic, referred to as "Black Death."
But the scientists have strong evidence to believe that "Black Death" was caused by gerbils, little rodents kept as pets, and that too from Asia where salubrious climate enabled them to survive along with their fleas.
Using Dendrochronology - the study of tree-ring records to glean about the past climates - the scientists found flea-infested gerbils populated in Central Asia in weather that alternated between wet spring and warm summer, and was invariably followed by a plague in Europe.
The flea-infested gerbils hitched a ride to Europe via the Silk Road and subsequently were responsible for the deaths of more than 100 million people in the "second plague pandemic," which began with the "Black Death" in the mid-14th century and recurred in the 1800s.
The scientists say the rats could not have caused the plague as the weather conditions in Central Asia were not favorable to them.
According to the study's authors, the plague didn't linger and went away, only recurring intermittently over the centuries, indicating that rats were not the culprits; if they were, the plague would have endured as long as rats were on hand to carry it.
"For this, you would need warm summers, with not too much precipitation," Nils Christian Stenseth, an author of the study, told Rebecca Morelle from the BBC. "We have looked at the broad spectrum of climatic indices, and there is no relationship between the appearance of plague and the weather."
The "Black Death" originated in China and is believed to have spread to medieval Europe along the Silk Road trade routes.
Last year, researchers, probing plague DNA in 25 fourteenth-century skeletons, said the plague was airborne rather than through flea bites.
Stenseth says his team will check those findings by analyzing DNA from ancient European skeletons. If the samples show significant genetic variation across time, that would indicate the outbreaks were caused by newly arrived waves of the disease rather than a resurgence from the continent's rat population.
The threat from bubonic plague continues even today. According to the World Health Organization, nearly 800 cases of plague were reported worldwide in 2013, including 126 deaths.
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