Where did rats originate? - briefly
The brown rat (Rattus norvegicus) and the black rat (Rattus rattus) both trace their origins to South and Southeast Asia, from where they spread globally via human commerce. Their ancestors diverged from other murine rodents in the late Miocene.
Where did rats originate? - in detail
Rats belong to the genus Rattus, which evolved within the Muridae family during the late Miocene, approximately 7–10 million years ago. Fossil evidence places the earliest Rattus species in Southeast Asia, particularly the region that now comprises modern‑day Thailand, Malaysia, and Indonesia. These early forms exhibit dental and skeletal characteristics that differentiate them from older murids, indicating a distinct evolutionary branch.
The two species most associated with human environments—Rattus norvegicus (the brown rat) and Rattus rattus (the black rat)—originated in separate Asian locales:
- Rattus rattus: native to the Indian subcontinent and surrounding islands; archaeological remains appear in ancient settlements of the Indus Valley and later in Egyptian contexts, suggesting early commensal relationships with humans.
- Rattus norvegicus: traced to the steppes of northern China and Mongolia; the species expanded northward and westward during the Holocene, reaching Europe through maritime trade routes.
Genetic analyses confirm a primary Asian ancestry for both species, with mitochondrial DNA indicating divergence roughly 1.2 million years ago. Subsequent dispersal patterns align with human migration and commerce:
- Ancient trade – Black rats spread across the Mediterranean aboard ships during the first millennium BC, establishing populations in ports such as Carthage and Alexandria.
- Medieval expansion – Brown rats entered Europe via overland routes from Siberia in the 18th century, later reaching the Americas on transatlantic vessels.
- Modern global distribution – Both species now occupy virtually every continent, thriving in urban, agricultural, and wild habitats.
Ecologically, rats adapted to a broad diet, high reproductive rate, and tolerance for varied climates, facilitating their successful colonization of human‑altered environments. Their origin in tropical and subtropical Asia, combined with later migrations linked to trade and settlement, explains the present worldwide presence of these rodents.