Stone tool‒makers ventured from Southeast Asia to the Indonesian island of Sulawesi deep in the Stone Age, far earlier than previously thought and probably before Homo sapiens originated in Africa 200,000 years ago, researchers say.
The discovery of ancient stone tools on Sulawesi, some of which date to as old as 194,000 years ago, also renews speculation about the evolutionary background of Homo floresiensis. Better known as the hobbit, H. floresiensis was a diminutive hominid that lived roughly 500 kilometers south of Sulawesi on the island of Flores at around the same time the Sulawesi tools were made.
“I wouldn’t be surprised if H. floresiensis or a closely related lineage was responsible for the Sulawesi artifacts,” says Harvard University archaeologist Christian Tryon, who did not participate in the new excavations. But the Sulawesi finds look much like stone tools made over the last 1.8 million years by several hominid species at sites throughout Southeast Asia, Tryon cautions. What’s certain, he says, is that Sulawesi hominids fractured stones to make sharp-edged cutting implements.
Hominids left stone tools at four sites located by a team led by archaeologist Gerrit van den Bergh of the University of Wollongong in Australia. Excavations at one site, Talepu, unearthed 315 securely dated stone artifacts. These sharp-edged rocks range in age from at least 194,000 years ago to about 118,000 years ago, the team reports online January 13 in Nature. Age estimates for the finds rest on calculations of the time since artifact-bearing soil was last exposed to sunlight.
Sulawesi and Flores are the only Southeast Asian islands known to have hosted hominids before modern humans reached several islands further east and Australia between 60,000 and 40,000 years ago. Homo sapiens arrived on Sulawesi roughly 40,000 years ago (SN: 11/15/14, p. 6).
Previous excavations on Flores led by archaeologist and study coauthor Adam Brumm of Griffith University in Nathan, Australia, uncovered 1-million-year-old stone tools made by presumed hobbit ancestors. Fossil discoveries indicate that hobbits lived from at least 190,000 years ago until perhaps 12,000 years ago.
As on Flores, no hominid fossils have been found with Sulawesi’s ancient stone artifacts, leaving the toolmakers’ evolutionary identity a mystery.
Several candidates for early Sulawesi colonizers exist, the researchers say. Hobbits or their ancestors may have floated over from Flores, as Tryon suggests. Neandertal-like Denisovans — a Stone Age population that lived in East Asia and left a genetic legacy in New Guinea, Melanesia and Australia (SN: 11/5/11, p. 13) — can’t be excluded. Or H. sapiens might have trekked from Africa to Sulawesi shortly after evolving in Africa.
There’s still another option. “Personally, I think Homo erectus is the most likely candidate,” van den Bergh says. H. erectus fossils range in age from 1.5 million to 140,000 years ago on Java, a nearby Indonesian island that was connected to Asia when sea levels periodically receded during the Stone Age.
Ancient H. erectus colonizers probably didn’t navigate the ocean in canoes or other vessels, van den Bergh holds. Instead, occasional tsunamis could have washed small numbers of H. erectus into the sea from Southeast Asia’s coast, he suggests. Southerly currents would have pushed castaways floating on vegetation or debris to Sulawesi. Accidental journeys of that kind probably explain how extinct elephants and other animals, known from fossil remains discovered in the new excavations and on previous expeditions, ended up on Sulawesi more than 200,000 years ago, van den Bergh adds.
It’s hard to know whether ancient Sulawesi hominids had already developed seagoing skills, says archaeologist Glenn Summerhayes of the University of Otago in Dunedin, New Zealand. “Colonization of an island by a new species is a process, not a single event, so multiple sea crossings would have been required,” he says.
Editor’s Note: This story was updated January 19, 2016, to correct the number of stone artifacts referred to from the Talepu site excavation.