The diminutive prehistoric human species dubbed the "Hobbit" that inhabited the isle of Flores apparently had company on other Indonesian islands long before our species, Homo sapiens, arrived on the scene.

Scientists on Wednesday announced the discovery of stone tools at least 118,000 years old at a site called Talepu on the island of Sulawesi, indicating a human presence. The scientists said no fossils of these individuals were found in conjunction with the tools, leaving the toolmakers' identity a mystery.

"We now have direct evidence that when modern humans arrived on Sulawesi, supposedly between 60,000 and 50,000 years ago and aided by watercraft, they must have encountered an archaic group of humans that was already present on the island long before," said archaeologist Gerrit van den Bergh of University of Wollongong in Australia.

The 2004 announcement of the discovery in a Flores cave of fossils of Homo floresiensis, a species about 3 feet 6 inches (1.1 meter) tall that made tools and hunted little elephants, jolted the scientific community.

"Like on Flores, where Homo floresiensis evolved under isolated conditions over a period of almost 1 million years, Sulawesi could also have harbored an isolated human lineage. And the search for fossil remains of the Talepu toolmaker is now open," van den Bergh said.

Scientists have been eager to unravel the region's history of human habitation. Sulawesi may have served as a stepping stone for the first people to reach Australia roughly 50,000 years ago.

"Major islands such as Flores, Sulawesi, Luzon, and perhaps others as well, could have served as natural experiments in human evolution, and could throw new light on human evolution in general," van den Bergh added.

The species that made the tools may have reached Sulawesi by drifting over the ocean on tsunami debris, he said.

The researchers described 311 stone tools, most made of a very hard limestone. Archaeologist Adam Brumm of Australia's Griffith University said they were produced by humans striking one stone with another, fashioning smaller pieces with knife-like sharpness.

"They mostly comprise simple sharp-edged flakes of stone that no doubt would have been useful for basic tasks like cutting up meat, shaping wooden implements, and so on," Brumm said.

Found nearby were fossils of an extinct elephant relative and extinct giant pig with warthog-like tusks.

The research was published in the journal Nature.