Rats get a bad rap, and deservedly so. They’re gross and carry a number of diseases.
And they’re infamously known for contributing to the spread of the Black Death, a plague pandemic that terrorized Europe in 1347 for five years and killed more than 20 million people.

Now, a new study is suggesting the possibility of a different scenario. The study proposes that human parasites like fleas and lice (also gross) were responsible for not only the spread of the plague, but the spread of a number of outbreaks from the 1300s to the 1800s (known as the Second Pandemic). Some historians have long believed rats were being unfairly blamed. According to the National Geographic:

For one, the Black Death tore through Europe far faster than any modern plague outbreaks. In addition, “rat falls” precede some modern outbreaks, but medieval plague records don’t mention rats dying en masse…If fleas and lice picked up the plague by biting an infected human, they could potentially hop onto a person in close quarters and transmit the disease.

The new study evaluated which model “best matched mortality patterns from nine different European plague outbreaks from the Second Pandemic. To their surprise, they found that in seven of the nine cities they examined, the human-parasite model more closely fit mortality records than the rat-flea model.”

What does this mean for the rats? Will their reputation be softened by this news? I lived for a number of years in a city fondly known as “Allston Rat City” nicknamed for its truly giant rats. On my street, rats were routinely run over, progressively flattened by cars until they became one with the road. It’s a cool party story I like to pull out. Everyone who has lived in Allston has at least two rat stories. I’ll spare you the second one.