Giant rats, some weighing as much as a small dog, roamed the jungles of East Timor alongside humans until about 1000 years ago, according to new findings from an Australian National University expedition.

The archaeologists discovered fossils from seven rat species, the largest known to have existed, during a project to determine when and how humans first travelled through and settled in South-east Asian islands.

The largest species discovered would have weighed up to five kilograms, about 10 times heavier than a modern rat.

One of the project's lead researchers, paleoanthropologist Julien Louys said there was evidence humans arrived on Timor at least 46,000 years ago, and co-existed with the rats until the end of the first millenium AD.

Dr Louys said such a long period of cohabitation with native species was unusual for early island-dwelling humans, who were notorious for wiping out endemic creatures.

"When humans get there [to unique island ecosystems], they're quite famous for wiping out a whole bunch of native species," he said.

"[Timor is] a very unusual situation for islands, because humans get to this island, but for 45,000 years they don't seem to have any significant impact on the diversity or the density of the species, and it's really only in the last thousand years or so that they're wiped out."

Bite and burn marks on the fossils show humans ate the giant rats through much of their history of habitation on Timor.

It's believed the megafauna died out when metal tools were introduced to the island, allowing humans to rapidly increase forest-clearing and construct defensive limestone "forts".

The rats themselves are understood to have arrived on the island 1 to 2 million years ago, after which Dr Louys said they would have started to grow larger thanks to the "island effect".

"The size increase is a very typical thing on islands, where traditionally small species would have grown larger and traditionally large species become smaller," Dr Louys said.

The team's findings were presented in the United States two weeks ago after returning from the East Timor expedition.

The project is part of Professor Sue O'Connor's investigation of initial human movement through South-east Asian islands en route to Australia, including their impact on ecosystems.

Dr Louys said the study, From Sunda to Sahul: Understanding modern human dispersal, adaptation and behaviour en route to Australia, built on an emerging field of research called conservation paleobiology, which uses fossil records to help inform modern sustainability and wildlife conservation.

It combines the fields of paleontology, archaeology and anthropology to discover past interactions between humans and animals.

"The fossil record gives us a unique and long-term picture of what happened in the past, so how animals responded to past periods of climate change, different levels of habitat disturbance and also how animals responded to the arrival of humans," he said.

The research teams are planning another expedition next year.