From what did rats originate? - briefly
Rats evolved from early muroid ancestors that diverged from other rodent lineages during the Oligocene epoch, about 30–35 million years ago. These primitive murid‑like mammals gave rise to the modern genus Rattus.
From what did rats originate? - in detail
Rats belong to the family Muridae, a lineage that emerged during the early Oligocene epoch, approximately 30–35 million years ago. Fossil evidence places the earliest murid rodents in Eurasia, where small, nocturnal mammals adapted to diverse habitats, including forests and open grasslands. These ancestors displayed the characteristic rodent dentition—ever‑growing incisors with a single enamel ridge—allowing efficient gnawing of seeds and fibrous plant material.
Key evolutionary developments that shaped modern rats include:
- Dental specialization – the development of continuously erupting incisors and the loss of canine teeth created a versatile feeding apparatus.
- Skull reduction – a compact cranium reduced body mass, facilitating maneuverability in tight spaces and burrows.
- Reproductive acceleration – short gestation periods and large litter sizes increased population growth potential, a trait retained by contemporary species.
Genus Rattus appeared later, in the Pliocene, around 3–5 million years ago. The two most widespread species, Rattus norvegicus (brown rat) and Rattus rattus (black rat), diverged from a common ancestor that inhabited tropical and subtropical regions of Southeast Asia. Molecular phylogenetics indicates that these lineages spread globally through human activity, exploiting ships, trade routes, and agricultural settlements.
Environmental pressures that drove diversification included:
- Competition for food resources, prompting opportunistic omnivory.
- Predation pressure, leading to heightened nocturnal activity and burrowing behavior.
- Climate fluctuations, encouraging adaptability to both temperate and arid conditions.
In summary, rats originated from early murid rodents that evolved specialized dentition, compact morphology, and rapid reproduction during the Oligocene. The genus Rattus emerged in the Pliocene in Southeast Asia, later expanding worldwide through anthropogenic dispersal, while retaining ancestral traits that underpin their ecological success.