Gerbils, Not Rats, Caused The Black Death Bubonic Plague Outbreaks: Study

For almost 800 years, history has blamed black rats for causing the catastrophic outbreaks of the bubonic plague in 14th-century Europe. They were long thought to have carried diseased fleas that jumped to -- and then infected -- more than 100 million people. But now, researchers have named a different furry creature as the Black Death culprit: gerbils. "If we're right, we'll have to rewrite that part of history," University of Oslo professor Nils Christian Stenseth told BBC News.

A study recently published in the Proceedings of the National Academy of Sciences journal found that climate conditions weren't right for rats to have spread the outbreak. Rats would have needed warm summers with little rain in order to thrive, Stenseth said, but data showed no relationship between spikes in plague cases and the weather.

Tree ring records indicate that Europe saw plague outbreaks whenever Central Asia had wet springs and warm summers. Those were great circumstances for rapid gerbil growth. "It means a high gerbil population across huge areas, and that is good for the plague," Stenseth told BBC News. He added, "We show that wherever there were good conditions for gerbils and fleas in Central Asia, some years later the bacteria shows up in harbor cities in Europe and then spreads across the continent."

Thriving rodents that had fleas with the plague bacteria, Yersinia pestis, would cross into Europe on the Silk Road. They were in a prime position to "wreak epidemiological havoc" until the 1800s, the Washington Post reported.

The discovery of the gerbil population's dependence on Asia's weather also may have solved the mystery of why the plague came in waves. Stenseth said his team will work to confirm this theory by checking their findings against DNA from victims' skeletons.

Although the black plague has mostly died out, about 780 people worldwide still contracted the disease in 2013, according to the World Health Organization. The three most at-risk countries were Madagascar, Peru and Congo.