For centuries, history books have pointed the finger at flea-infested black rats as the primary culprits behind the Black Death, the devastating plague that wiped out nearly 60% of Europe’s population in the 14th century.
The story has been passed down for generations: rats, scurrying through filthy medieval streets, carried infected fleas that spread the disease like wildfire.
But what if we’ve been blaming the wrong creature all along?
A new study published in the Proceedings of the National Academy of Sciences suggests that rats might not have been responsible at all.
Instead, the real spreaders of the bubonic plague may have been gerbils—yes, those small, seemingly harmless rodents from Asia.
The research, conducted by a team from the University of Oslo, examined climate patterns and historical data from the 14th to the 19th centuries and found that the conditions required for a rat-driven outbreak simply didn’t match reality.
“For this, you would need warm summers, with not too much precipitation,” explained study author Nils Christian Stenseth to the BBC.
“We looked at the broad spectrum of climatic indices, and there is no relationship between the appearance of plague and the weather.”
So, if it wasn’t rats, how did the Black Death and subsequent outbreaks keep returning to Europe? The answer lies thousands of miles away, deep in the heart of Central Asia.
Did Gerbils Really Spread the Plague? The Climate Data Says Yes
To unravel the mystery of how the plague repeatedly appeared in Europe over centuries, the researchers analyzed 7,711 historical plague outbreaks and compared them with 15 tree-ring climate records from the same periods.
What they found was astonishing:
- Every major plague outbreak in Europe was preceded by a warm, wet spring in Central Asia.
- These conditions were disastrous for black rats but ideal for another rodent—Asian gerbils.
- The timing of the outbreaks matched the movement of traders along the Silk Road, bringing infected gerbils and their fleas into Europe.
This means that rather than an ongoing rat infestation keeping the plague alive within Europe, the disease was likely reintroduced multiple times by infected rodents arriving from Asia.
And the real shocker?
The pattern repeated for nearly 500 years, explaining why outbreaks occurred sporadically instead of persisting continuously.
The Myth of the Plague-Infested Rat
For centuries, the belief that rats spread the Black Death has been almost unchallenged.
Medieval illustrations even depicted rats as sinister creatures symbolizing death and disease.
The idea became so ingrained that it shaped public health policies—leading to efforts to eradicate rats in many cities.
But let’s pause for a moment.
If rats were responsible for the plague, why didn’t the disease remain constant in Europe?
This is where the gerbil theory provides a compelling counterpoint.
If rats had been the primary carriers, the plague would have persisted year-round rather than arriving in waves, disappearing, and then reappearing decades later.
Instead, what we see in historical records is a clear pattern:
- Plague outbreaks always followed climate shifts in Asia, not changes in European rat populations.
- Black rats were common in Europe for centuries—but the plague was not.
- The plague arrived in Europe in cycles, just as trade routes became more active.
This challenges one of the longest-standing medical assumptions in history.
What This Means for Our Understanding of Epidemics
If the Black Death wasn’t a rat-borne disease, it changes the way we think about how pandemics spread.
- History needs a rewrite. After 800 years of wrongly accusing black rats, researchers may need to reexamine other historical pandemics to see if their origins have also been misunderstood.
- The role of climate change in disease transmission is more significant than we thought. If climate shifts in Asia repeatedly triggered the arrival of the plague in Europe, could other diseases today be following a similar pattern?
- Disease doesn’t always spread the way we assume. While we often think of pandemics as spreading from person to person, this research shows that they can also be reintroduced from distant ecosystems repeatedly over time.
Could DNA Evidence Prove This Theory?
Of course, not everyone is convinced that gerbils were the primary spreaders of the plague.
Some scientists argue that black rats may still have played a secondary role, particularly in urban outbreaks.
To settle the debate, the researchers are now turning to DNA evidence.
By analyzing genetic material from plague victims buried across Europe, they hope to track mutations in the bacteria over time.
If they find significant genetic changes between outbreaks, it would suggest that new strains were repeatedly introduced from outside sources (like gerbils) rather than lingering in European rat populations.
“If we’re right, we’ll have to rewrite that part of history,” said Stenseth.
For now, it seems likely that black rats have been wrongfully blamed for one of history’s deadliest pandemics—and gerbils may be the true villains behind the Black Death.
After all, history is written by survivors. But sometimes, even the facts need a second look.
Sources:
BBC, The Washington Post, Proceedings of the National Academy of Sciences
