Where do rats come from? - briefly
Rats trace their ancestry to Asia: the brown rat (Rattus norvegicus) evolved from wild steppic populations in Central Asia, while the black rat (Rattus rattus) originated from African and Indian lineages that later spread worldwide. Their global distribution resulted from human trade and settlement patterns that facilitated their expansion.
Where do rats come from? - in detail
Rats belong to the genus Rattus, which evolved from murid ancestors during the late Oligocene to early Miocene, approximately 23–30 million years ago. Fossil evidence shows early members of the Muridae family spread across Eurasia, giving rise to several lineages that later diversified into the species recognized today.
The two most widespread species, the brown rat (Rattus norvegicus) and the black rat (Rattus rattus), originated in distinct regions:
- Brown rat – native to the steppes of Central Asia, especially the region that now includes Mongolia and northern China. Adaptation to human‑altered environments allowed rapid expansion across Europe and North America during the 18th and 19th centuries.
- Black rat – traced to the Indian subcontinent and Southeast Asia. Maritime trade routes facilitated its spread to the Mediterranean, Africa, and the Americas beginning in the 1st millennium CE.
Key mechanisms of global distribution include:
- Maritime transport – ships provided shelter, food, and nesting sites. Rats boarded vessels in their native habitats and disembarked at ports, establishing colonies in new territories.
- Agricultural development – grain storage and cultivated fields offered abundant resources, supporting population growth and encouraging settlement in rural areas.
- Urbanization – dense human settlements created continuous habitats with waste and shelter, enabling rats to thrive in cities worldwide.
Genetic studies reveal low mitochondrial diversity among worldwide populations, confirming recent, human‑mediated dispersal rather than ancient, natural colonization. The brown rat’s adaptability to colder climates and its larger size contributed to its dominance in temperate regions, while the black rat remains more common in tropical and subtropical zones.
In summary, rats originated from murid ancestors in Eurasia, diverged into distinct species with separate geographic roots, and achieved a worldwide presence through human activities such as shipping, agriculture, and urban development.