How many years have rats existed? - briefly
Rats first appeared in the fossil record during the Oligocene epoch, roughly 23 million years ago. Their lineage has persisted continuously to the present day.
How many years have rats existed? - in detail
Rats belong to the family Muridae, which emerged during the early Miocene epoch. Fossil evidence places the earliest murid rodents at approximately 23 million years ago. The genus Rattus, which includes the common brown and black rats, appears later in the fossil record, first documented around 2 million years ago in the Pleistocene.
Key points in the evolutionary timeline:
- Early Miocene (≈23 – 16 Ma): Diversification of murid ancestors; small, generalized rodents spread across Eurasia.
- Late Miocene to Pliocene (≈11 – 2.5 Ma): Emergence of several murid lineages; adaptation to varied habitats.
- Early Pleistocene (≈2 Ma): First appearance of Rattus species; morphological features similar to modern rats.
- Holocene (last 10 000 years): Global expansion facilitated by human activity; domestication and commensalism with humans.
Molecular clock studies corroborate the fossil data, estimating the split between the Rattus lineage and its closest relatives at roughly 1.5 – 2 million years ago. Consequently, rats as a distinct group have existed for about two million years, while their broader murid ancestors have a history extending over twenty million years.