A small fragment of bone represents the final piece of a puzzle that has taken academics working on opposite sides of the globe almost two decades to solve.
The ancient fossil is part of a shin bone that was found in 1921 at the Broken Hill mine in Zambia and is thought to belong to a Homo heidelbergensis man, an ancestor of modern human beings.
The bone resides in the Natural History Museum in London, where a staff member cut a small triangular chunk out of it for analysis.
And leading anthropologist Chris Stringer arrived in Canberra on Sunday with it in his carry-on luggage.
He is working at the Australian National University with long-time collaborator Rainer Grun to date the bone using the university's state of the art technology.
Professor Stringer said the Broken Hill site was particularly significant because the bones found there, including the well-known Broken Hill skull, are thought to be about 250,000 years old, far younger than the 500,000 years attributed to other bones from the same species.
He said there were Homo sapiens bones dated to a similar period, opening up the possibility modern humans and their ancestors once lived side by side.
The shin bone, found just a metre from the skull, is the last fossil from the site left to be dated. ''This will help us tell whether it is really the same individual. Hopefully we get the same age result. If we don't we're in trouble,'' he said.
Professor Stringer said Homo heidelbergensis were more strongly built than modern humans with a smaller average brain size than people today.
They were hunter gatherers who made stone tools and hunted large mammals, deer, horses and maybe even rhinoceros.
Professor Stringer said the project of dating various elements from the site began in 1994, with several different researchers involved in the process.
When the bone was buried it took uranium into it, which then decayed, and its age could be determined by tracking that process of decay, he said.
Professor Grun said as the technology available to researchers had dramatically improved over time and researchers had new ideas on how to best understand the fossils, the Broken Hill project had been extended.
''It never came to a point that we were happy to publish … it's always, 'Oh, we could do this','' he said.
Professor Stringer began work on the Broken Hill project in 1994 with another researcher, who has since retired.
Professor Grun and other academics have since contributed to the work.
The pair have been collaborating since they met at a conference in the 1980s.
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