Geochemical ‘stamp’ offers new hope for repatriation of unprovenanced human remains

A team of researchers have investigated geochemical signatures in surface geology and ancient remains as a potential tool to repatriate Indigenous skeletons back to their place of origin.

Dr Michael Westaway, PhD candidate Shaun Adams, Professor Brian Fry and Professor Rainer Grun, from Griffith’s Australian Research Centre for Human Evolution, led the team that has built an isotopic geochemical reference framework for Cape York, QLD, that can aid in refining the regions of origin for collected ancestral remains that have no known provenance.

The findings have been published in GeoArchaeology.

The team looked at the ratio of two strontium (Sr) isotopes (87Sr/86Sr) in archaeological and environmental material recovered throughout Cape York and built a series of maps, developed with Traditional Owner groups, that reveals where people may have grown up, lived and been buried.

Adams said investigating the isotope chemistry of tooth enamel offered the chance to measure a robust geochemical signature, that does not degrade as quickly as biological material in Australia’s harsh environment.

“We also utilised tooth enamel because it records the place of childhood and retains the signature for thousands of years,” he said.

“However, before Sr isotopes in human teeth can be used to determine provenance, we must first know how Sr in the landscape varies.”

For the study, the team sampled water, plants and soil, and compared that to faunal teeth to approximate what human Sr isotope results should look like.

These Sr isotopes weather from rock into soil and water, where they are taken up by plants, animals and humans. Sr from rocks passes through water, animals and humans without change and leaves a ‘stamp’ on remains.

“So we are not just ‘what we eat’ but also ‘where we eat’,” Adams said.

“Our bodies become an isotope record of where we have been and what we have eaten. This makes them especially useful in archaeological projects hoping to understand prehistoric human mobility and diet.

“By looking at teeth, we can see where people grew up and then compare that to the bones, which take on the variable signature and can reveal where they were buried.

“Teeth and bone are strong proxies for where someone has lived. Our map shows the variability of Sr isotope ratios throughout Cape York is wider than that seen in oversees studies.”

Adams said that Sr isotope ratios will reveal some of the regions that ancestral remains have come from, but as there is often more than one place with the same results he suggested it as a tool that could be used to narrow down results.

“This technique is bolstered by combining with genetics and other morphometric techniques that look at the physical characteristics of humans,” he said.

The technique has been used globally for decades and was successfully used to resolve the provenance of ancestral remains from Victoria back in 2004.

The work was advised by the Cape York Aboriginal Advisory Committee, which was set up to offer advice on repatriation for his Australian Research Council Linkage Grant: LP140100384. It comprised of Indigenous representatives from throughout Cape York.

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