By Paul Rincon

BBC News science reporter



We've got the prospect of having other new species of human on various parts of island South-East Asia

Mike Morwood, University of New England

Since last year, the remains of at least nine individuals have been found in a cave on the Indonesian island.

The discovery team has now excavated more than 500 stone tools from another, much older, site about 40km away.

They believe a population ancestral to the Hobbits may have lived at this site, which is 850,000 years old.

"At Mata Menge there are hundreds and hundreds of in situ stone artefacts with Stegodon fossils," Mike Morwood, director of the excavations, told the BBC News website.

Extended stay

The skeletal remains of Homo floresiensis, as they are more properly called, were all unearthed from cave deposits at Liang Bua on Flores.

There is evidence these people inhabited the site from perhaps 100,000 to 12,000 years ago.

Unlike modern humans, H. floresiensis has little in the way of a chin

Yet stone tools found at both sites are small and well-crafted, Professor Morwood said.

At another site in the Soa Basin of central Flores, the researchers have found evidence that hominids were living on the island by one million years ago.

The announcement last year detailing a single, partial skeleton from Liang Bua caused a sensation when it was claimed to be a human species new to science.

The individual was found to have been only a metre tall, earning its nickname of Hobbit after the small characters from the Lord of the Rings books.

This week, Professor Morwood and his team published details in the academic journal Nature of more remains found at the cave, including an individual about five years old who was only 50cm tall.

Pandora's box

The discoveries at Liang Bua and elsewhere on Flores have "opened a Pandora's box of possibilities", according to Professor Morwood.

"If we've got hominids on Flores, we've almost certainly got them on Timor, because there are reports of Stegodon fossils associated with stone tools there," he explained.

"So we've got the prospect of having other new species of human on various parts of island South-East Asia. Some of them could be really weird, having adapted to specific island environments."

It is still not known how hominids travelled by sea between these islands. Building watercraft may have been a skill too far for them.

So natural catastrophes such as tsunamis have been invoked by some researchers to explain their distribution. Hominids could have clung to trees as they were washed out to sea, eventually arriving on the shores of other islands.

Revised ancestry

The researchers had thought the Hobbit's island-hopping ancestor was Homo erectus, which is known to have lived on nearby Java.

But some now think it could have been an earlier hominid known as Homo habilis. If so, it raises the possibility that hominids colonised South-East Asia at least two million years ago.

Unfortunately, it looks unlikely that genetic material will be extracted from the remains dug from Liang Bua thus far. This could have sealed the case for the Hobbit as a new species, rather than a modern human pygmy or diseased individual - as some researchers have suggested it is.

"DNA does not seem to have been preserved in the remains we have," Professor Morwood explained. "That's partly to do with the conditions in the cave but partly to do with the way the material was treated during excavation.

"We cleaned it, in some cases washed it and handled it. If we were doing it again now, the material would be taken out in its soil matrix, put in a plastic bag and kept cool. That way your chances of retrieving DNA go right up."

DNA is often preserved within teeth, and can be recovered by drilling inside one. But Professor Morwood said the H. floresiensis teeth recovered from Liang Bua were too scientifically valuable to allow them to be drilled.