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Stone tools recently discovered on the Indonesian island of Sulawesi are rewriting the story of the early human occupation of island Southeast Asia.
Perhaps the most famous hominin from this region is Homo floresiensis (the ‘Hobbit’), a small-statured species found on the island of Flores. The oldest H floresiensis remains date to 100,000 years ago, but other evidence indicates that an early hominin species was present on the island as far back as 1.02 million years ago. Meanwhile, findings on the island of Luzon in the Philippines have identified the presence of a different small-bodied species (Homo luzonensis) dating to 700,000 years ago. In contrast, the oldest archaeological indication of early humans on Sulawesi dated to just 194,000 years ago, until now.
Excavations at a site called Calio, in southern Sulawesi, were carried out by a joint team from Indonesia and Australia between 2019 and 2022. They unearthed seven Early Pleistocene tools: all chert flakes that had been struck from larger stones using hard-hammer freehand percussion (below). Palaeomagnetic dating of the sediments where the tools were found, combined with uranium-series and electron-spin resonance (US-ESR) of fossilised pig teeth excavated from the same layer, indicate that the tools date to at least 1.04 million years ago, and possibly up to 1.48 million years ago. These findings reveal that hominins reached Sulawesi significantly earlier than previously known, placing their arrival around the same time or even before the early hominins on Flores, and well before Luzon.
The identity of the makers of the tools at Calio remains a mystery, as no associated hominin fossils have been found. The question also remains, how did they reach Sulawesi? Even when sea levels were at their lowest, the island was at least 50km from the nearest Asian landmass; this would have been too far to swim, particularly with the strong ocean currents, but it is unlikely too that these early hominins had the cognitive ability to plan and build seafaring vessels. The researchers therefore believe that it is most likely that these early humans arrived on Sulawesi in the same way that other species are believed to have done so: by accident – for example, on natural rafts of floating vegetation.
The research has been published in Nature (https://doi.org/10.1038/s41586-025-09348-6).
Text: Amy Brunskill / Image: M W Moore