Waikato University's Dr Fiona Petchey at work in the
radiocarbon dating lab. The lab has dated a batch of
samples from an Aboriginal site in Australia to 35,000 years
ago.
Photo by Barker Photography

Waikato University's radiocarbon dating lab is at the heart of a discovery that Aboriginal people lived as many as 35,000 years ago in Western Australia.

The university's radiocarbon dating lab has dated four samples of charcoal from the site - a mine site in Pilbara, northwest Australia - to confirm there was human occupation at the site 35,000 years ago. The lab is now dating a further 10 samples to refine that chronology, and expects to report back to the archaeologist and researcher by the end of June.

The findings indicate it is one of the oldest sites in Australia. It is internationally significant as a prehistoric record of humanity.

Radiocarbon dating can be used to determine the age of a sample as far back as 60,000 years, by measuring the amount of Carbon-14 - originally formed in the upper atmosphere through the activity of cosmic rays and subsequently taken up by plants and animals. When the plant or animal dies, the Carbon-14 slowly decays away. The amount of Carbon-14 in what remains indicates its age.

The lab's deputy director, Dr Fiona Petchey, said the work in question would help with national and international understanding of the early occupation of Australia.

Waikato University, one of only two radiocarbon dating lab sites in New Zealand, has done work in the past for Boone Law, the American archaeologist involved in overseeing the Western Australian dig.

The carbon samples from the Pilbara site came from a rock shelter with artefacts which showed human activity, and evidence of fires - most likely campfires. "It could be natural fire, but he does say that the charcoal occurs with cultural material," Dr Petchey said.

She said the site was perfect from a radiocarbon dating perspective in that it was perfectly layered and appears to have been undisturbed for generations; several samples had been taken from the oldest layers to ensure dating accuracy; and younger and older samples from the same rock shelter could also be used to help refine the dates.

The staples for radiocarbon dating were charcoal, wood, shell, bone and peat, but Dr Petchey said staff have had to date hair, paper and bird vomit. "Basically, the weirder the sample gets, the more risk you are taking that it holds up to testing."

The radiocarbon dating lab, which has operated at the University of Waikato since the early 1970s, tests about 1500 samples a year. The lab is funded by research and commercial activities.

The samples are predominantly from New Zealand, Australia and UK sites. Dr Petchey said the lab had been particularly popular with UK archaeologists because of the international reputation of the lab and good customer service.

A lot of the New Zealand work came from middens, while the British were still digging up material from old houses, Roman sites and Iron Age days, she said.