Where did rats originate on Earth? - briefly
Rats first evolved in Asia, with fossil evidence pointing to origins in the region of present‑day China and Southeast Asia. From there the genus Rattus spread worldwide through natural migration and human‑facilitated dispersal.
Where did rats originate on Earth? - in detail
Rats belong to the genus Rattus within the family Muridae, a lineage that emerged from early murid rodents during the Oligocene epoch, roughly 30–35 million years ago. Fossil evidence places the earliest murids in Asia, with specimens recovered from the Siwalik Hills of the Indian subcontinent and from paleontological sites in China. Molecular phylogenies consistently identify Southeast Asia, particularly the Indo‑Malayan region, as the primary cradle of the Rattus radiation.
Key evolutionary milestones include:
- Late Miocene (≈10 Ma): Appearance of the first recognizable Rattus‑like fossils in southern China, indicating an early diversification of the genus in humid tropical environments.
- Pleistocene (≈2 Ma – 12 ka): Expansion of several Rattus lineages across mainland and island Southeast Asia, driven by fluctuating climate and the development of forest corridors.
- Holocene (≈10 ka onward): Emergence of the two most widespread species—Rattus rattus (black rat) and Rattus norvegicus (brown rat). Genetic analyses trace R. rattus to the Indian subcontinent and nearby islands, while R. norvegicus shows a lineage rooted in northern China and Mongolia.
Human activity accelerated global distribution. R. rattus spread along maritime trade routes from the Indian Ocean to the Mediterranean by the first millennium CE. R. norvegicus followed overland and via ships from East Asia into Europe during the 18th century, eventually supplanting R. rattus in many temperate regions.
In summary, the ancestral home of rats lies in the tropical and subtropical zones of Asia, with subsequent diversification and worldwide dissemination closely linked to both natural climatic shifts and human‑mediated transport.