Where did rats originate from? - briefly
The genus Rattus first arose in Southeast Asia about two to three million years ago. Human commerce and settlement subsequently spread the animals across the globe.
Where did rats originate from? - in detail
Rats belong to the genus Rattus, which emerged in the late Miocene epoch, about 10–12 million years ago, in the region that now comprises South and Southeast Asia. Fossil evidence from the Siwalik Hills of India and the Chinese province of Yunnan confirms the early presence of Rattus species in these tropical environments. The two most widespread species—Rattus norvegicus (brown rat) and Rattus rattus (black rat)—originated from distinct lineages within this Asian cradle.
- R. rattus developed in the Indian subcontinent and the surrounding archipelagos; its adaptation to human settlements facilitated rapid expansion across the Indian Ocean.
- R. norvegicus evolved in the temperate zones of northern China and Mongolia; it later spread northward into Siberia and eastward into Japan.
Human maritime activity accelerated global dissemination during the medieval and early modern periods. Ships traveling from Asian ports to Europe, Africa, and the Americas carried rats as unintended cargo, establishing feral populations on new continents. By the 18th century, both species were entrenched in major port cities worldwide, exploiting human waste and grain stores.
Genetic analyses of mitochondrial DNA reveal low diversity among global rat populations, indicating recent colonization events linked to trade routes. Contemporary distribution patterns reflect historical human movement more than natural dispersal, with R. norvegicus dominating temperate urban centers and R. rattus persisting in warmer, coastal regions.