Black rats may not have been responsible for the numerous outbreaks of bubonic plague in medieval Europe, a new study suggests.
Scientists instead say that giant gerbils from Asia were responsible for causing the plague, known as the Black Death, which proved to be one of the deadliest outbreaks of disease in human history.
"If we're right, we'll have to rewrite that part of history," Professor Nils Christian Stenseth, from the University of Oslo, told the BBC.
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It was previously thought that black rats were responsible for spreading the bubonic plague, and that huge plague reservoirs existed in Europe. However, "our analysis finds no support for the existence of permanent plague reservoirs in medieval Europe", the researchers suggest.
The study found that, rather than "a single introduction at the time of the Black Death", the pandemic was caused by "a climate-driven intermittent pulse of new strains arriving from Asia".
The giant gerbils are thought to have carried the disease across the land and sea routes of the Silk Road, with their fleas passing the disease on to humans.
"We show that, wherever there were good conditions for gerbils and fleas in central Asia, some years later the bacteria showed up in harbour cities in Europe and then spread across the continent," said Professor Stenseth.
His team found that warm and wet weather conditions in Asia caused gerbil numbers to boom. "Such conditions are good for gerbils. It means a high gerbil population across huge areas and that is good for the plague," he added.
The team of scientists now plan to carry out extensive tests on plague bacteria DNA taken from ancient skeletons.
Europe has not experienced an outbreak of the plague since the end of the 19th century, but the disease continues to spread in other parts of the world. No British cases have been reported since 1918.
