How many years have rats been on Earth? - briefly
Rats have been present on Earth for roughly 23 million years, according to Miocene fossil records. Their lineage traces back to early murine rodents that first appeared in that epoch.
How many years have rats been on Earth? - in detail
Rats belong to the family Muridae, which is part of the order Rodentia. The rodent lineage first appears in the fossil record during the early Eocene, roughly 56 million years ago. Within this broad group, the subfamily Murinae (the “true mice and rats”) emerges in the late Miocene, about 12–10 million years ago. Fossils attributable to the genus Rattus—the group that includes the common brown and black rats—are dated to the Pliocene, approximately 3–2 million years ago. Modern species such as Rattus norvegicus (the brown rat) and Rattus rattus (the black rat) spread worldwide after the advent of human seafaring, roughly 1 – 2 thousand years ago.
Chronological summary
- ~56 Mya: First rodents appear.
- ~12–10 Mya: Murinae subfamily originates.
- ~3–2 Mya: Genus Rattus emerges.
- ~1–2 kya: Global distribution facilitated by humans.
Thus, the ancestors of today’s rats have existed for tens of millions of years, while the specific rat genus has persisted for a few million years.