The discovery of layers of grass ash stretching back 25,000 years suggests that a cave in south-eastern Australia was home to elaborate rituals for over 1000 generations of Indigenous inhabitants.
Cloggs cave is in the homeland of the GunaiKurnai people in south-eastern Victoria. In 2024, archaeologists and traditional owners announced the discovery of ancient artefacts inside the cave, providing evidence for the extraordinary possibility that a ritual had survived for 12,000 years through to modern times.
Now, at Monash University in Melbourne, along with , a GunaiKurnai elder, and their colleagues have uncovered evidence that more than doubles the amount of time that cultural practices took place in the cave. The purposes of these rituals are thought to have included magic, healing and cursing.
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The team found thousands of microscopic, silt-sized preserved cells called phytoliths that form when plants absorb soluble silica from the soil and deposit it within their structures. Grasses were the dominant vegetation type, making up 97 per cent of the burnt phytoliths found in the cave.
David thinks this is because grasses immediately turn to ash, rather than charcoal, when burnt, and the ash was considered important for ceremonies.
These phytolith fossils indicate that people had brought whole grasses including their roots into the cave and burnt them to repeatedly make thin layers of ash, he says.
The researchers were then able to link this practice of burning ashes with cultural practices described by the Alfred Howitt. In the 1880s, in other parts of GunaiKurnai country Howitt recorded the ceremonies of powerful medicine men and women that he described as 鈥渨izards鈥�. His accounts show that ash was an important part of GunaiKurnai rituals in the 19th century.
鈥淪uch burning of grass goes back to 25,000 years ago inside the cave, but between 4400 and 1600 years ago, the burning of ash layers became more frequent and more widespread across the floor of the cave,鈥� says David.
Around 2000 years ago, a standing stone was erected in the cave and over the next 400 years, grass was burnt all around it.
Unlike pollen, which can be transported by wind, phytoliths are usually deposited immediately beside the plants from which they originate. The team also ruled out the possibility that the fossils were washed in by a flood.
The cave also contained phytoliths deposited in the scats of common brushtail possums (Trichosurus vulpecula), but these were unburnt, distinguishing them from the phytoliths created by human activities.
The ashes weren鈥檛 always associated with the same kinds of archaeological remains, suggesting they were created by a range of practices in the cave, says David.
鈥淭he common theme here is that people repeatedly piled grasses and burnt them,鈥� he says. 鈥淧rior to 4400 years ago, the bringing and burning of grass into the cave was more sporadic and less frequent, not resulting in the repeated dense ashy layers that we see after 4400 years ago, although other kinds of ritual activities involving stalactites and miniature fires with single fat-smeared sticks were performed during those earlier times.鈥�
at the Australian National University in Canberra says archaeobotanical research has been underrepresented in Australian archaeology, which has meant that a 鈥渓arge portion of past life has been understudied鈥�.
鈥淭his is a great study, weaving careful scientific analysis of phytoliths with GunaiKurnai cultural knowledge to show that grasses were specially collected and burnt at Clogg鈥檚 cave to support ritual practices over many millennia,鈥� says Florin.
Frontiers in Environmental Archaeology
