• Needle in a haystack: The tiny figure of archaeologist Charlie Dortch against these cliffs show the task he faces unearthing ancient artefacts. Despite years of searching, just eight have been found on Rottnest Island. Photos supplied
ARCHAEOLOGISTS are narrowing in on the earliest human contact with Rottnest Island, and say the age of prehistoric artefacts they’ve discovered should bring greater respect to Noongars.
A team of seven archaeologists including Fremantle father-and-son team Charlie and Joe Dortch, are on the brink of submitting their findings to the journal Australian Archaeology next month.
The elder Dortch says the discovery of stone tools lodged in bands of limestone allowed the group to date the earliest known human contact with the island using a technique called optically stimulated luminescence (OSL).
While they’ve only been able to narrow that date to somewhere between 17,000 and 42,000 years, Dr Dortch says previous estimates based on circumstantial evidence have led to wild claims.
• It’s tiny, but clearly made by humans and embedded in rocks formed thousands of years ago.
Shell “middens” had even been the subject of a couple of PhDs, with claims they were evidence of Aboriginal occupation. That was debunked when it was discovered the debris had been left behind by Pacific gulls that no longer visited the island.
No charcoal linked to humans has been found on Rotto, meaning radio-carbon dating isn’t possible.
OSL measures radioactivity stored by grains of quartz as isotopes nearby decay after burial.
Dr Dortch says they’ll be able to hone in even further as dating techniques improve.
Intriguingly, a tiny fragment of emu eggshell found near one of the stone tools was dated as 28,000 years old by the University of Colorado. The shell is the only vertebrate fossil ever to be found on the island.
Dr Dortch says despite being found near the stone tool, he can’t tell how it came to be on the island.
“It was only about the size of a little fingernail, so I was very lucky to even find it,” he says.
Prehistoric human contact with Rottnest would have to predate the island’s separation from the mainland around 10,000 years ago when sea levels rose, as Noongars did not use boats.
Oral histories make reference to the separation of Rottnest, Garden and Carnac Islands, all of which are considered to have great spiritual significance.
Dr Dortch says the findings will help Noongars overcome a perception held by some that the south-west was unoccupied, and strengthen their kinship with the land.
Finding artefacts in-situ has allowed the team to date them for the first time.
Pibulmun elder Wayne Webb agrees: “What I thank Charlie for is showing non-Aboriginal people that, in the south-west, the Pibulmun/Wadandi lived and thrived, and helping dispel the myth that the real Aboriginal people live above the 26th parallel and those of us in the south-west do not exist.”
Dr Dortch says just eight artefacts have been found on the island, but their research has identified other areas he says warrant a dig.
One is a series of wetlands that once held fresh water, but have been saline since the Rottnest Island Authority churned them up while searching for road-building material in the 1960s and ‘70s.
by STEVE GRANT