New climate data suggests rats probably didn’t transmit the Black Death and murder millions – but gerbils are the perfect candidates.

Rats have a pretty bad rap among rodents, and it’s largely thanks to the Black Death. Believed to have been carried by rats and transferred to humans by fleas, the Black Death killed up to 200 million Europeans, forever giving them a reputation as filthy disease carriers. Now a new study published in the Proceedings of the National Academy of Sciences has put forward the theory that gerbils – not rats – were responsible for the countless deaths that drastically changed the populations of Europe.

Follow me on this journey: The Black Death originated in Asia, reaching Europe in 1347 and killing millions across several epidemics. Scientists generally believed that rats were the responsible carriers – but new climate research suggests the conditions weren’t ideal for large rat reservoirs. “For this, you would need warm summers, with not too much precipitation. Dry but not too dry,” Professor Nils Christian Stenseth from the University of Olso explained. “And we have looked at the broad spectrum of climatic indices, and there is no relationship between the appearance of plague and the weather.”

Professor Stenseth and his team made this conclusion by comparing European tree ring records with rings from 7711 historical plague outbreaks. The results prompted Stenseth to consider another option – that a wet spring followed by a dry summer caused gerbil and flea populations to increase in Asia before moving to Europe.

“Such conditions are good for gerbils. It means a high gerbil population across huge areas and that is good for the plague,” he continued. “To me this was rather surprising … Suddenly we could sort out a problem. Why did we have these waves of plagues in Europe? We originally thought it was due to rats and climatic changes in Europe, but now we know it goes back to Central Asia.”

Of course, that doesn’t mean rats can’t carry diseases – just that they may not be responsible for one of the worst outbreaks in history. And yet gerbils are considered perfectly normal pets while rats – which tend to be quite friendly and intelligent when domesticated – horrify people on sight.

Although I suppose gerbils being pretty freaking adorable certainly helped that view.

Source: PNAS, via BBC

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