US anthropologist Frank M. Setzler dug up the remains of Aboriginal people all over the area - as he had also done with native Americans - in the name of science.

Those stolen remains were kept at the Smithsonian Institute in Washington.

It was the darker side of a celebrated event: the 1948 American-Australian Scientific Expedition to Arnhem Land.

Australian National University historian Martin Thomas learned of the theft - which he said was illegal - while doing research in 2006 when he met elder Jacob Nayinggul from the Gunbalanya indigenous community.

Nayinggul and others were distressed about what had happened and lobbied for years for the return of the bones.

Former ambassador to the US Kim Beazley also helped until a reluctant Smithsonian eventually agreed.

Dr Thomas documented the campaign including the trip by three men from Arnhem Land to Washington to collect the bones and conduct a smoking ceremony.

Dr Thomas has made a film, Etched in Bone, about the story that could not be completed until recently for cultural reasons, due to the deaths of indigenous people featured.

It includes footage of Mr Setzler on camera as he pretends to make a "surprise" discovery of bones in a burial cave and culminates in an emotional ceremony conducted by Mr Nayinggul in which the remains are buried again in Gunbalanya.

"Stealing people's bones and taking them away to study, well, it's no bloody good," Mr Nayinggul says in the film, which was screened for Gunbalanya locals on the town's football field this month.

Mr Nayinggul, who died within a year of the bones being returned in 2011, wanted people to hear the story and use it as a model for the repatriation of the remains of indigenous people around the world, says co -producer of the film Beatrice Bijon.

The screening was a proud moment for the children and extended family of Mr Nayinggul, who spent much of his life in the service of Aboriginal Australians, including helping set up the local Njanjma ranger group.

"We are very proud, it is great that the grandkids can see what he went through. He was a strong man, an elder who helped a lot of people," his daughter Connie said.

Like the tomb of the unknown soldier, the identities of the stolen Arnhem Land remains are unknown but can be dated back to around 1900.

"For a lot of scientists, archaeologists at that time, that's just what you did. There wasn't that level of cultural understanding about the incredible offence this was causing," Dr Thomas said.

"According to the indigenous belief system, you are really messing with the spirit world, wrenching spirits out of their communities."

Australian Associated Press