Ancient tools on Sulawesi may be clue to origins of ‘hobbit’ hominins

Seven stone tools found on the Indonesian island of Sulawesi are the earliest evidence ever discovered of ancient humans making a sea crossing, dating back up to 1.4 million years.

They may provide clues to how a tiny human species, nicknamed “hobbits”, ended up on the nearby island of Flores.

The first of the artefacts was found embedded in a sandstone outcrop at a site called Calio by Budianto Hakim at the National Research and Innovation Agency in Indonesia in 2019, and a full excavation uncovered six more tools in the same outcrop.

In the same deposit as the stone tools, Hakim and his colleagues found part of the upper jaw, with teeth, of an extinct giant pig known as Celebochoerus, along with a tooth fragment from an unidentifiable species of juvenile elephant.

While the researchers couldn’t directly date the stone tools, they were able to come up with an estimated age of between 1.04 million and 1.48 million years old by analysing the sediments and the fossil pig’s teeth. Until now, evidence of hominins on Sulawesi only stretched back to 194,000 years ago.

At least one of the newly discovered artefacts is a flake that was struck off a larger flake and then had its edges trimmed, says team member Adam Brumm at Griffith University in Brisbane, Australia. While non-human primates like chimpanzees have been known to use stones like a hammer to break open nuts, they don’t carefully work flakes to produce tools.

“This is a very early kind of human intelligence from a species that no longer exists,” says Brumm. “We don’t know what species it was, but this is a human intelligence behind these stone artefacts at the site of Calio.”

The remains of a metre-tall hominin named Homo floresiensis were discovered on Flores in 2003. Archaeological evidence shows that hominins were on that island more than 1 million years ago, but it has been a mystery how an early human species could have made their way there.

Both Flores and Sulawesi had large expanses of sea separating them from mainland South-East Asia, even during the periods of lowest sea levels. Brumm says the distances between the mainland and Sulawesi were too great to swim and it is almost certain that these early hominins weren’t capable of building ocean-going vessels.

“It may have been some sort of freak geological event, like a tsunami, for example, washing some hominins out to sea clinging to floating trees or vegetation mats of some kind, and then winding up on these islands in large enough numbers to give rise to these isolated populations,” he says.

Martin Porr at the University of Western Australia says Homo erectus was the most likely candidate to have made the sea crossings, as this species was in South-East Asia at this time and made tools similar to those found in Sulawesi.

He says while the new work is consistent with this hypothesis, it also raises many new questions, especially whether the capabilities of these early hominins need to be revised.

The late archaeologist Mike Morwood, who led the team that identified Homo floresiensis, was the first to suggest that Sulawesi was an important place to search for potential ancestors of the hobbits, says Kira Westaway at Macquarie University in Sydney, Australia. This is due to the path of the Indonesian throughflow, a strong current that flows from Sulawesi to Flores.

“But I think that even Mike would be pleasantly surprised by the antiquity of the stone tools found at this site,” she says. “It could be argued that seven tools is not a large enough assemblage to support large claims, but it certainly represents an early hominin presence.”

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