The Unlikely Story of Rats: From Ancient Asia to Global Dominance

From scurrying through ancient civilizations to becoming indispensable lab animals, the story of rats is deeply intertwined with human history. These adaptable creatures have navigated ice ages, plagues, and urban expansions, proving themselves to be one of the most successful invasive species on Earth. Let's delve into the fascinating journey of rats and their impact on our world.

The Origins and Early Spread of Rats

The tale begins roughly 1 to 3 million years ago in Asia, where the ancestors of today's common rat species first emerged. These resourceful rodents survived the last ice age and eventually began coexisting with humans. Their adaptability earned them a place in the Chinese zodiac, symbolizing new beginnings.

• Generalists by Nature: Rats are biological generalists, meaning they can thrive in diverse climates and adapt to various diets. This trait played a crucial role in their global spread.
• Early Travelers: As trade routes opened between East Asia and the West, rats seized the opportunity to expand their territory, hitching rides on ships.

Black Rats: The First Explorers

Black rats were the first to venture out, traveling from India to Egypt around 5,000 years ago. Some historians believe their arrival in Egypt may have even contributed to the ancient Egyptians' reverence for cats, who were, after all, excellent rat catchers.

• European Arrival: Trade between Egypt and the Roman Empire facilitated the spread of black rats into Europe. By 300 CE, they had reached as far as the Anglo-Celtic Isles.
• Disease Carriers: Unfortunately, black rats also carried bacterial and viral infections, spreading diseases like the plague through their droppings and urine.

The Black Death and the Rise of Brown Rats

The Black Death, one of history's most devastating pandemics, swept through Europe in the late 1340s, killing millions. While rats were initially blamed, the reality is more nuanced. Black rats carried fleas that transmitted the bacterium responsible for the plague, but they weren't directly responsible for spreading the disease to humans.

Meanwhile, in Japan, brown rats were gaining popularity as pets. Guidebooks from 250 years ago detailed how to domesticate them and breed them for desirable traits.

The Arrival of Brown Rats in Europe

Brown rats arrived in Europe between the 13th and 18th centuries, traveling by ship and, in some cases, even swimming. Legend has it that a violent earthquake in 1727 drove hordes of brown rats to swim across the Volga River into Russia.

• Outcompeting Black Rats: The larger and more adaptable brown rats eventually displaced black rats in homes and cities across Europe and North America.
• Industrial Revolution Boost: The Industrial Revolution provided brown rats with new opportunities, as they thrived in the expanding cities, making homes in sewers and feasting on trash.

Rats in Science: A Monumental Turn

The human-rat relationship took a significant turn in 1906 when the Wistar Institute in Philadelphia bred the first standard rat strain for scientific research. Rats became invaluable lab animals due to their physiological similarities to humans and their intelligence.

• Unrivaled Lab Animals: Rats' bodies function similarly to humans, and we share much of the same genome, making them ideal for studying diseases and testing treatments.
• Neuroscience Pioneers: Their intelligence has made them indispensable to neuroscience and psychology research. Studies in the 1960s, for example, demonstrated that rats raised with toys and companions had thicker cortical brain tissue, contributing to the understanding of neuroplasticity.

The Rat Race Continues

Today, rats are considered one of the most successful invasive species in the world. However, this success comes at a price, as they often live at the mercy of human priorities. In cities like New York, they are reviled and targeted with multi-million-dollar extermination efforts.

Despite our efforts to control them, history suggests that we will never fully rid ourselves of our rodent shadows. The story of humans and rats is a long and complex one, filled with disease, adaptation, and even scientific breakthroughs. As we continue to shape the world around us, rats will undoubtedly continue to adapt and thrive alongside us.