A new study suggests that the long-held belief that black rats were responsible for transmitting the bubonic plague across Europe may not be true.

The black rat has long been maligned as the transmission agent for one of the deadliest outbreaks of disease in human history. The Black Death arrived in Europe in the mid-14th century, and killed millions of people during a series of epidemics over the course of the the next 400 years.

Gerbils, Not Rats, Responsible For Black Death

Asian gerbils transmitted Black Death

Scientists have long believed that the Black Death originated in Asia, and was then transmitted by black rats in Europe when fleas jumped from rodent to human. However a new study has made them reconsider its origins. The Black Death is now thought to have been transmitted by gerbils in Asia, and Professor Nils Christian Stenseth, from the University of Oslo, claims that: “If we’re right, we’ll have to rewrite that part of history.”

In order to disprove the popular plague theory, the scientists studied tree-ring records from Europe and the weather conditions during thousands of historical plague outbreaks in order to determine whether conditions could have encouraged an outbreak of the Black Death driven by rats.

If this were to occur “you would need warm summers, with not too much precipitation. Dry but not too dry,” said Stenseth. The team concluded that there was no correlation between plague outbreaks and the weather.

Silk Road brought plague to Europe?

However they do believe that a set of specific weather conditions in Asia could have led to the flourishing of populations of the giant gerbil, another plague-carrying rodent. This in turn could have led to the European epidemics.

“We show that wherever there were good conditions for gerbils and fleas in central Asia, some years later the bacteria shows up in harbour cities in Europe and then spreads across the continent,” Prof Stenseth said.

Stenseth claims that the Black Death was most probably carried to Europe along the silk road, which was used to transport goods between the two continents at a time when trade was at a peak.

In order to back up their new theory, the team will analyze plague bacteria DNA from skeletons. If there is a large amount of variation it would suggest that different waves of plague arrived from Asia.