Dyani Lewis
Dyani Lewis is a freelance science journalist based in Melbourne, Australia.
Opinions among archaeologists are divided over an 11-year investigation of an Australian site containing what could be an ancient midden, or shell heap.
If it is, in fact, the result of human activity, dating evidence pushes back the likely arrival of people into the island continent to 120,000 years ago – almost double the current confirmed estimate.
The Moyjil-Point Ritchie site the southern coast near the mouth of the Hopkins River has intrigued scientists since the early 1980s because of its scattered deposits of sea snail shells. Questions of Moyjil’s archaeological significance have swirled around the site ever since.
The new research – published in a series of papers in the journal Proceedings of the Royal Society of Victoria – pins down the antiquity of the shell deposits, using three different methods.
But analysis of the shells and the rocks they are associated with doesn’t definitively point to whether the collection of shells is an ancient human midden or the work of sea birds.
Theories differ – even among those who have worked at the site.
“I’m now 99% convinced that people were there,” says geologist Jim Bowler from the University of Melbourne, who has studied the Moyjil site since the 1980s. But, he concedes, “it lacks confirmatory evidence”.
The earliest undisputed evidence of humans in Australia is from the Madjedbebe rock shelter in northern Australia. Sediments containing stone hatchet heads, grinding stones and other artefacts were dated to 65,000 years ago
Stretching that date back to 120,000 years – which would imply the arrival of seafaring people from Asia during a period of low sea levels some 10,000 years earlier again – is a leap too far for many.
“It seems to me extremely unlikely that this is human habitation,” says archaeologist Chris Clarkson from the University of Queensland, who excavated the Madjedbebe site but was not involved in the current study.
“Given that the burden of proof is extremely high for something like this, I think we just have to dismiss it as being natural accumulations,” he says.
Significantly, no human artefacts – stone tools or butchered bones, say – have been uncovered at Moyjil.
Nevertheless, archaeologist Ian McNiven from Monash University maintains it would be premature to declare the case closed.
“Superficially, it does look cultural,” he says. “The shells look like an Aboriginal midden. The burnt patches of rocks look like they could be hearths. But it’s not enough to make the call on it.”
McNiven excavated one of two hearth-like structures at Moyjil. While it could be a bona fide hearth, he says, more work is needed.
Analysis of the charcoal suggests that it comes from root wood. This could mean that instead of a prehistoric fireplace, the scientists may have found nothing more than a tree stump that caught fire millennia ago. Some of the classic layering that has been found at some, although not all, other hearths is also absent, notes McNiven, and other processes such as decaying of algae are known to blacken rocks along that stretch of coastline.
“We need to make sure whether the stones that I excavated,” he notes, “have been blackened by burning or some other process. We haven’t actually demonstrated that yet.
“Given the enormous age here, we have to make a very strong case with hard evidence that it is human and that it’s not natural.”
In the next phase of the study, McNiven will excavate the second hearth-like section with a specialist from Boston University in the US and conduct a microstructure analysis of the sediment for further clues about its origins.
“It can’t be left hanging,” says McNiven. “It’s just too important, so we have to throw all the science we can at it.”
