Stone tools, animal bones, and decorative beads unearthed on a remote tropical island in the northern gateway to Australia are helping to build a picture of how people lived there more than 17,500 years ago.

The discoveries, on the small Indonesian island of Obi, include the earliest evidence in the region of a particular stone tool technology, edge-ground axes, dating back 14,000 years. Obi, a densely forested 2,500km2 island, was one of the destinations previously plotted on a ‘treasure map’ developed by CABAH researchers to identify the stepping-stones Aboriginal people used to get to Australia

The rugged volcanic island is located in a region historically renowned for trade in spices like nutmeg, mace, and cloves that may also contain preserved evidence of modern people moving across Indonesia to the super-continent of Sahul more than 50,000 years ago. However, the archaeology of the region is largely unexplored.

What was found?

3kg+ of bone — 80 % cuscus, along with lizards, snakes, turtles, fish and bats. Plus 1.3kg of shells — almost all marine shells

Artefacts also included:

A red ochre crayon and shark bones and Oliva shells — which were used as decorative beads.

Early people

The results of the first excavations on Obi, published today in PLOS ONE, offer exciting insights to the technologies and diets of people living there during three phases of occupation dating back to before the last Ice Age.

CABAH investigators, from The Australian National University, collaborated with local people and Indonesian colleagues from Universitas Gadjah Mada and ARKENAS during fieldwork on Obi in 2019. Together they excavated two rock shelter sites near the village of Kelo.

Detailed analysis of the artefacts discovered at the two sites provided the first evidence that people were living on the island up to 18,000 years ago. The preserved artefacts, and the depths at which they were found, also help to piece together a bigger picture of both the development of technology and the capabilities of these early people.

“Until now, the island of Obi has never been explored by archaeologists, making every discovery all the more exciting and significant,” said Dr Shimona Kealy. “Learning about how people lived on Obi in the past and how they may have interacted with neighbouring island communities can help us to reconstruct these ancient communities, their technological capabilities, and how they responded to change.”

Stone tools

The team found evidence of distinctive edge-ground axes, which require a high level of skill to shape, dating back approximately 14,000 years. These tools were traditionally used in the region for the construction of watercraft, in particular dugout canoes.

Dr Ceri Shipton, an expert in stone tools who was part of the team, said: “It’s possible that the early appearance of these tools on Obi also coincided with the advent of dugout canoes and, therefore, greater marine capabilities for these early peoples.”

Lead researcher Professor Sue O’Connor says: “With luck, we might find some answers to the apparent gap in occupation after 8,000 years, and maybe even extend the record of human occupation on Obi even deeper into the past.”

Edge-ground axe from Kelo — showing the sharpened tip of this tool. Image credit: ANU

Edge-ground axe from Kelo — showing the sharpened tip of this tool.

Image credit: ANU

Bones recovered during the investigations suggest that cuscus — a relative of the brush-tailed possum — was a popular food source in Obi’s past, a hunting practice that continues today.

“As the forests became more dense during the early Holocene, the people of Kelo likely relied on the use of axes for hunting cuscus,” Dr Kealy says.

Dr Shipton adds: “Historical records from New Guinea indicate that ground stone axes were traditionally used to make clearings to get clear shots at cuscus, to make notches for climbing trees to get at cuscus, or to cut down branches on which cuscus were hiding.”

Sharing technologies

The researchers also suggest that the people of Kelo brought technologies with them from the broader Wallacea region.

The Obi story thus far is based on inland sites and the researchers plan to return, when possible, to excavate more coastal sites.

Dr Shimona Kealy recording features of the stratigraphy during excavations at Kelo 6.