Ancient tools found on Sulawesi suggest early humans crossed formidable seas over a million years ago, leaving behind mysteries about their identity and evolution.
Researchers from Griffith University have uncovered evidence that early hominins ventured across open seas to reach the Indonesian island of Sulawesi far earlier than previously believed. The discovery comes from stone tools at the Early Pleistocene (or ‘Ice Age’) site of Calio, dated to at least 1.04 million years ago.
The study, published in Nature, was led by Budianto Hakim of Indonesia’s National Research and Innovation Agency (BRIN) and Professor Adam Brumm of the Australian Research Centre for Human Evolution at Griffith University.
Hakim’s excavation team unearthed seven stone artifacts from sandstone layers exposed in a cornfield in southern Sulawesi. These tools provide direct evidence of early human activity in the region.
During the Early Pleistocene, the Calio site would have been an active setting for tool production and related behaviors such as hunting, located near a river channel that likely supplied both resources and raw materials.
The Calio artefacts consist of small, sharp-edged fragments of stones (flakes) that the early human tool-makers struck from larger pebbles that had most likely been obtained from nearby riverbeds.
Establishing the Age
The Griffith-led team used palaeomagnetic dating of the sandstone itself and direct-dating of an excavated pig fossil, to confirm an age of at least 1.04 million years for the artefacts.
Previously, Professor Brumm’s team had revealed evidence for hominin occupation in this archipelago, known as Wallacea, from at least 1.02 million years ago, based on the presence of stone tools at Wolo Sege on the island of Flores, and by around 194 thousand years ago at Talepu on Sulawesi.
The island of Luzon in the Philippines, to the north of Wallacea, had also yielded evidence of hominins from around 700,000 years ago.
“This discovery adds to our understanding of the movement of extinct humans across the Wallace Line, a transitional zone beyond which unique and often quite peculiar animal species evolved in isolation,” Professor Brumm said.
“It’s a significant piece of the puzzle, but the Calio site has yet to yield any hominin fossils; so while we now know there were tool-makers on Sulawesi a million years ago, their identity remains a mystery.”
Who Were the Early Inhabitants?
The original discovery of Homo floresiensis (the ‘hobbit’) and subsequent 700,000-year-old fossils of a similar small-bodied hominin on Flores, also led by Professor Brumm’s team, suggested that it could have been Homo erectus that breached the formidable marine barrier between mainland Southeast Asia to inhabit this small Wallacean island, and, over hundreds of thousands of years, underwent island dwarfism.
Professor Brumm said his team’s recent find on Sulawesi has led him to wonder what might have happened to Homo erectus on an island more than 12 times the size of Flores?
“Sulawesi is a wild card – it’s like a mini-continent in itself,” he said.
“If hominins were cut off on this huge and ecologically rich island for a million years, would they have undergone the same evolutionary changes as the Flores hobbits? Or would something totally different have happened?”
Reference: “Hominins on Sulawesi during the Early Pleistocene” by Budianto Hakim, Unggul Prasetyo Wibowo, Gerrit D. van den Bergh, Dida Yurnaldi, Renaud Joannes-Boyau, Akin Duli, Suryatman, Ratno Sardi, Indah Asikin Nurani, Mika Rizki Puspaningrum, Irfan Mahmud, Afdalah Haris, Khairun Al Anshari, Andi Muhammad Saiful, P. Arman Bungaran, Shinatria Adhityatama, Putra Hudlinas Muhammad, Anwar Akib, Nani Somba, Fakhri, Basran Burhan, Zubair Mas’ud, Mark W. Moore, Yinika L. Perston, Wenjing Yu, Maxime Aubert and Adam Brumm, 6 August 2025, Nature.
DOI: 10.1038/s41586-025-09348-6
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4 Comments
Um, in a region that seems to move more than 1 cm per year, 1 million years suggests even a 10,000 km gap could have started out with less than a 1 cm gap. So, how do they know that the intrepid ancient ones actually made long harrowing sea journeys?
{o.o}
Im insanely curious to know… what proof is there that humans made and used these shards? How do we know these pieces haven’t been naturally broken and eroded to look like this? Just because it looks a little bit like an arrowhead doesn’t mean it actually is…
Stones have layers of material in them. When a stone breaks naturally, it breaks mostly along those layers. Not so for tools crafted by humans.
A natural break generally has no symmetry. Crafted tools generally do.
There can also be other marks where the shard was sharpened.
Erosion makes all edges smoother – so cannot produce sharp edges like naturally broken stones and human crafted shards.
All that said, a single shard can be mischaracterized as human crafted when it was really created naturally. However, when you have multiple of them in a single location – the likelihood of them being hand-crafted goes up.
1 000 000cm is 10 km. not 10 000km.
Homo erectus is known from Java and has been for some time; the fossils have been dated at about 1 00 000 years. Therefore, H erectus could certainly put to sea. The use of hollowed-log canoes, especially if used as catamarans, would readily enable sea-travel. H erectus was around for about 1 million years , so perhaps stone tools on Sulawesi should not seem so surprising. If hominims got to Sulawesi 1 million years ago, why not PNG and Australia?