Using chemistry to uncover the past

Chemical isotope analysis is a powerful technique - Dr. Charlotte King explains to Claire how she uses it to reconstruct past lives of forgotten people from the Otago gold rush.

Our skeleton, our nails, our tissues, are all made from basic chemical elements. These elements pass from the soil, to growing plants, to the food we eat and into our bodies. By following this pathway backwards, one researcher is learning about the lives of some forgotten people of the Otago gold rush.

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In a small lab in the Department of Anatomy at the University of Otago, research fellow Dr. Charlotte King is carefully photographing a piece of bone, teeth and some hair. She is documenting them before she takes a small section to do her research - chemical isotope analysis.

Charlotte is part of the Southern Cemeteries Archaeology project - a group of researchers working with local communities who were concerned about unmarked graves related to the gold fields of central Otago.

The project has run over several years and has involved excavations of unmarked graves at several cemetery sites in Milton, Lawrence and Drybread. Once human remains are recovered, many lines of evidence are used by the team to reconstruct where these people came from and how they lived.

The aim is to learn about them, and their lives in the Otago gold fields, before they are reburied in marked sites.

Charlotte is investigating the ratios of isotopes of different chemical elements in the human tissues recovered. Because different chemical isotope signatures are present in different rocks, soils and food, Charlotte can use this to uncover clues as to where the people were from and what kinds of food they ate at different times during their lives.

Learn more:

A previous Our Changing World episode was recorded at the archaeological dig in Milton.

The Drybread cemetery dig was reported on with several interviews at the time:

On Nights, before the excavation

Morning report

Checkpoint

The project's website contains further information about their findings

The Southern Cemeteries Archaeology project is co-lead by Prof. Hallie Buckley and Dr. Peter Petchey. The excavations at Drybread cemetery were done in consultation with, and permissions from, the Drybread Cemetery Trust and Leslie and Maisie Wong of the Otago-Southland Chinese association.

Go to this episode on rnz.co.nz for more details