PARIS – Scientists have discovered stone-age tools at least 118,000 years old on an Indonesian island but no trace of the early humans that made them, according to a study released Wednesday.
The research, published in the journal Nature, also points to a possible link with the first peoples to arrive in Australia.
Unearthed at four sites on Sulawesi, the trove of several hundred implements is likely to fuel a long-simmering debate about the identity of the human species that first came to the island chain.
In 2003, fossil remains from a diminutive species of hominin — a term that groups extinct lineages of early man and modern humans — was discovered on the neighboring island of Flores.
Dubbed the “Hobbit,” Homo floresiensis had arrived there at least a million years earlier, dating tests revealed.
The new find shows “that Flores was not the only island once inhabited by archaic humans before Homo sapiens” — modern man — “got there around 50,000 years ago,” said lead author Gerrit van den Bergh, a researcher at the University of Wollongong in Australia.
The Hobbit, many scientists say, is a descendant of the extinct species Homo erectus that became smaller across hundreds of generations, a process called “insular dwarfing,” whereby animals — after migrating across land bridges during periods of low sea level — wind up marooned on islands as oceans rise.
“The fossil fauna associated with the Hobbit and the stone artifacts clearly indicate isolated island conditions,” van den Bergh explained.
“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 said.
Other scientists had argued that Flores man, as it is sometimes called, might have had distinct origins, and a few had even suggested it was a tribe of modern humans suffering a genetic disorder resulting in an abnormally small skull. But both of these notions have been largely dismissed.
Whether the makers of the Sulawesi tools are also derived from Homo erectus — which lived in nearby Java at least 1.5 million years ago — is impossible to know without fossil evidence.
But the new discovery, van den Bergh said, raises the intriguing possibility of a link with the earliest humans to populate what is today Australia.
“We know from genetic evidence that the first people coming to Australia, and their descendants, have a tiny proportion of their DNA inherited from an enigmatic group of humans called the Denisovans,” he said.
Related to both human and Neanderthal lineages, Denisovans are thought to have split off from the former about 600,000 years ago, and the latter some 400,000 years later. They survived until at least 40,000 years ago.
Fossil records of the Denisovans are so meager — a few teeth and a pinkie bone excavated from a cave in Siberia — that scientists don’t even know what they might have looked like.
But the DNA link with Australia’s original inhabitants strongly suggests that some made their way deep into Asia.
“The genetic exchange between the ancestors of the modern Australians and Denisovans probably took place somewhere in Southeast Asia,” van den Bergh said. “It could well be that the makers of the recently dated stone tools from Sulawesi could have been these Denisovans.”
Unfortunately, DNA does not survive nearly as well in tropical climes as in frigid Siberia, so the chances of finding genetic clues are diminished.
One thing that is certain, the study said, is that the tools were not made by Homo sapiens. “They are just too old for that,” van den Bergh said.
The sharp-edged tools — single- or double-faced — were made by chipping flakes away from a piece of very hard limestone.
Archaeologist Adam Brumm of Australia’s Griffith University said 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.”
Found nearby were fossils of an extinct elephant relative and extinct giant pig with warthog-like tusks.