How the Brown Rat Quietly Spread Across the World

Why It Matters

Understanding the brown rat’s global spread and rapid urban adaptation informs smarter pest‑control policies and urban design, reducing health risks and ecological side‑effects as cities confront climate change.

Key Takeaways

• Brown rats originated in Northeast Asia, showing greatest genetic diversity there.
• 18th‑century maritime trade spread rats to Europe and US coasts.
• Genetic and archaeological data link North American rats to a 1760 shipwreck.
• Rats form single‑lineage colonies, resisting newcomers and limiting genetic influx.
• Urban settings drive rapid dietary, morphological, and metabolic rat adaptations.

Summary

The video explores how the brown rat (Rattus norvegicus) expanded from its native Northeast Asian range to become a global urban pest. Researchers combined genetic sequencing, ancient DNA techniques like ZooMS, and historical records to map the species’ movements, revealing that the highest genetic diversity—and thus the likely origin—lies in eastern Asia. Key findings show that rats left Asia roughly 800‑1,000 years ago, spreading southward along coastlines and possibly via the Silk Road, but the dominant pathway to Europe and the Americas was maritime. A sunken merchant ship from 1760 provides the earliest solid evidence of the species in North America, and genetic data suggest two independent introductions to the Atlantic and Pacific coasts. Examples highlighted include the single‑lineage colonies that dominate urban populations, the skull‑shape changes observed in New York City rats, and isotopic studies showing diet shifts from wild seeds to human waste. These adaptations illustrate rapid evolutionary responses to diverse climates and food sources. The research underscores that effective rat management must consider their biology, social structure, and the built environment. As cities grow and climate change alters habitats, rats are poised to become even more entrenched, making informed, ecologically‑aware control strategies essential for public health and infrastructure.

Original Description

The brown rat has spread to almost every continent around the world. But how did it get here? And are they here to stay?

Read the review: https://www.science.org/doi/10.1126/science.adp1166