Cool Finds

1.04-Million-Year-Old Stone Tools Found on Indonesian Island Offer Clues About Some of the Region’s Earliest Human Relatives

The toolmakers or their ancestors might have arrived on Sulawesi by clinging to vegetation during a storm, but their identities remain a mystery

Margherita Bassi | Daily Correspondent

August 21, 2025

Share

Copy linkEmailSMSFacebookXRedditLinkedInBlueskyPrint

Add as preferred source

Archaeologists working on the Indonesian island of Sulawesi have excavated stone tools dating to at least 1.04 million years old. The artifacts represent another puzzle piece in the enigmatic history of hominins—the group including modern humans, extinct human species and close human ancestors—in Wallacea, the islands between the Asian and Australian landmasses.

Prior to this discovery, the oldest stone tools found on Sulawesi dated to about 194,000 years ago. This finding pushes that date back by hundreds of thousands of years. But exactly who made the tools—and how their makers reached the island in the first place—are still open questions.

The team, led by Budianto Hakim, a researcher from the National Research and Innovation Agency of Indonesia, and Adam Brumm, an archaeologist from Griffith University in Australia, described the discovery in a paper published earlier this month in the journal Nature.

Previously, stone tools on the much smaller Indonesian island of Flores indicated that hominins lived in Wallacea starting at least 1.02 million years ago. The hominins on Flores were strange, however—fossils of the island’s resident species, Homo floresiensis, commonly referred to as hobbits, indicate that they were very small, standing just over three feet in height.

The new findings suggest hominins might have inhabited Sulawesi before reaching Flores. “Our new study reveals the first evidence a sea crossing to Sulawesi may have happened at least one million years ago. That’s much earlier than previously known and means humans reached here at about the same time as Flores, if not earlier,” write five of the researchers in an article for the Conversation.

Hakim, Brumm and their colleagues uncovered seven stone tools at the Early Pleistocene site of Calio in southern Sulawesi. Today, the site is near a corn field, but back then, it was next to a river. The tools consist of sharp stone fragments, called flakes, shaped from larger pebbles that the hominins likely gathered from the riverbed.

“We don’t know what they were doing with these sharp-edged flakes of stone, but most likely they were cutting or scraping implements of some kind,” Brumm tells National Geographic’s Tim Vernimmen.

To infer the age of the tools, the team dated the sandstone rock that surrounded them, as well as a pig fossil excavated nearby. They found that the layer was at least 1.04 million years old—and potentially up to 1.48 million years old. Because archaeologists have yet to find early hominin fossils on Sulawesi, however, they don’t know who the toolmakers were.

“So far, the oldest human skeletal element found anywhere on this island is a modern human maxilla [upper jaw] fragment that is around 25,000 to 16,000 years old,” Brumm tells Live Science’s Kristina Killgrove. “It would be premature to assign a hominin species to the toolmakers” before finding archaic hominin fossils on Sulawesi, he adds.

Several questions still stand regarding early hominins’ journeys from mainland Asia to the Wallacean islands. Martin Porr, a paleolithic archaeologist from the University of Western Australia who was not involved in the study, tells New Scientist’s James Woodford that Homo erectus likely made the sea crossing, given that the species existed in Southeast Asia during this time and made similar tools to the ones found at Calio. In the Conversation, the research team also suggests it was Homo erectus that made the crossing and that the species subsequently evolved to be smaller after living on islands.

As for how hominins crossed the sea, the oceanic distance between the Asian mainland and Sulawesi would have been too far to swim, per the Conversation. At the same time, these hominins likely wouldn’t have had the ability to build seafaring vessels. Instead, the researchers suggest they made it across by accident, potentially on raft-like masses of floating vegetation.

“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,” Brumm tells New Scientist.

On Flores, a population of hominins could have evolved into the so-called hobbits. So, what would have happened to those that landed on Sulawesi? The hominins might have grown to resemble Homo floresiensis, or they could have changed in completely different ways on the much larger island. It remains to be seen what artifacts will provide the next puzzle piece.

Margherita Bassi | Read More

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.