The biggest rat to walk the earth was 10 times the size of the rats we know today, or about the size of a small dog. It was discovered alongside seven other giant rat species in 2015 in East Timor, a Southeast Asian country occupying the eastern half of Timor Island. Only two of the recently unearthed species have been formally described by science. The island, which is shared with Indonesia, was home to many large species during the late Quaternary period (0.5 million to one million years ago).

The largest of the rats appeared at Timor approximately one to two million years ago, and coexisted with humans there for about 45,000 years. Burns and cut marks on the bones indicate that people ate the rats. They were probably also preyed upon by large raptors, giant monitor lizards, smaller monitor lizards, and large pythons.

The longstanding relationship between the rats and their human predators is notable. Human beings have historically been quick to wipe out prey on small islands.

The species eventually became extinct about 1,000 years ago, which is around the time that metal tools were introduced on the island. Researchers speculate that the tools greatly accelerated the rate of deforestation, reducing the animals' habitat and leaving them with fewer places to hide. This theory is supported by the fact that all but two of Timor's indigenous mammals died out during the same period.

Oversized rats still exist today on the Southeast Asian islands of Papua New Guinea, Flores, and the Philippines. However, these species top out at 6.6 pounds. By underscoring the importance of preserving forests, the new discovery may protect them from suffering the same fate that befell their forebears.

The discovery and analysis of the rat remains is part of the Australian National University's "From Sunda to Sahul" archaeological research project, which is studying the earliest human movement through Southeast Asia. The team shared the find in a presentation entitled "Holocene Extinction of Timor's Endemic Giant Murid Community, and Implication for Modern Murid Conservation on Islands" at the 2015 Meeting of the Society of Vertebrate Paleontology.

Learn about more gigantic animals from the Earth's past.