Until recently archaeological evidence suggested humans had occupied the ACT for about 21,000 years - since the time of the last Ice age.

But new advances in dating technology prove that Aboriginal people have actually lived in the ACT region for much longer.

Archaeologist Josephine Flood in 1999 at the site of Garnawala in Wardaman country, west of Katherine in the Northern Territory ( Supplied: Dr C. Chippindale )

The oldest human remains to be found in Australia are at least 40,000 years old - but there are academics that say Australia may have been occupied long before this.

In the ACT, evidence of Aboriginal occupation extends back more than 20,000 years.

Proof of this was discovered at Birrigai rockshelter in Tidbinbilla in the 1980s, by archaeologist Josephine Flood.

When the artefacts she found were first dated, they were found to be about 21,000 years old – around the time of the last Ice age.

A recent breakthrough in dating technology has shown they are in fact 25,000 years old.

"We found human occupation," Dr Flood said.

"Not a lot of it, but enough to tell us that humans had been using that rock shelter from 25,000 years ago.

"The earliest tools and charcoal ... was dated to 25,000 years – right up to historic times at the end of the 19th century. The 1890s."

Written evidence indicates the relationship between the traditional owners and the white settlers was initially friendly, however there are accounts of violent confrontations.

European diseases also had a devastating impact on the Aboriginal community.

As described in Dr Flood's book, Moth Hunters of the Australian Capital Territory, within 50 years of white settlement in the ACT, the Aboriginal population had declined significantly – primarily because of illnesses like measles, whooping cough and influenza.

Dr Flood said Birrigai may have been used by local Aboriginals, to avoid contact with white settlers.

"There was rabbit bone in the top and the people obviously retreated there when the Europeans moved into what is now Canberra," she said.