Where are rats from? - briefly
The brown rat (Rattus norvegicus) evolved in the Indian subcontinent, and the black rat (Rattus rattus) originated in Southeast Asia. Both species later spread globally via human commerce.
Where are rats from? - in detail
Rats originated in Asia, with the two most common species tracing distinct evolutionary paths. The brown rat (Rattus norvegicus) evolved from ancestors that inhabited the steppes of Central Asia, while the black rat (Rattus rattus) descended from populations native to the Indian subcontinent and surrounding islands.
- Fossil evidence places early Rattus species in the Pleistocene deposits of Mongolia and northern China, dating back roughly 1.5 million years.
- Molecular phylogenetics confirms a divergence between the two lineages around 1–2 million years ago, aligning with climatic shifts that opened new habitats across Eurasia.
- The brown rat spread westward through trade routes into Europe during the 18th century, eventually colonizing North America via ships arriving in the early 1700s.
- The black rat followed maritime pathways earlier, reaching the Mediterranean, the Middle East, and later the Americas by the 16th century, aided by grain storage on vessels.
Human activity accelerated global distribution. Grain shipments, ship ballast, and urban waste created favorable conditions for colonization, allowing both species to establish populations on every inhabited continent except Antarctica. Contemporary surveys show the brown rat dominating temperate regions, while the black rat persists in tropical and subtropical areas, often cohabiting with human settlements.
Genomic studies reveal low genetic diversity within introduced populations, reflecting founder effects from limited numbers of individuals transported by trade. Nonetheless, rapid adaptation to diverse climates and diets demonstrates the genus’s remarkable ecological flexibility.