Lighting Up Archaeological Science

What sparked your interest in science and analytical chemistry in particular?
 

I’ve always been interested in natural materials, ancient cultures, and archaeology, and, as a high schooler, wondered how I could use analytical science to understand the past. Mr Tony Kardis, my chemistry teacher in high school, introduced me to the world of spectroscopy by demonstrating the changes in electronic state in gasses and how to use a diffraction grating to view the atomic spectra. He continued to be my mentor and advisor as I worked on independent research projects analyzing historic ceramics from the 1904 St Louis World’s Fair. From this point, I attended several local and state science fairs, and the International Science and Engineering Fair, and the rest, as they say, is history.

How did you get into archaeological science?
 

The intersection of physical sciences and social sciences is highly interesting to me and archaeological science naturally expands the frontiers and benefits of both. In my undergraduate and graduate degrees, I studied analytical chemistry and spectroscopy, as well as field archaeology in several locations around the world, which ultimately led to a career in analytical chemistry-based archaeological science. With both field and lab experience, I’m fortunate to work across both disciplines and I’m very grateful for all the opportunities, supervisors, and interdisciplinary projects that have supported my career thus far. 

What are the main challenges for analytical scientists working in the archaeological space?
 

Objects and artifacts are often looked at in isolation – especially if they’re based in a museum or collection site outside of the excavation. However, when we examine cultural heritage items, we analyze at a microscopic level while also looking at the entire object and where it fits in the cultural landscape. Our archaeological science lab group at the University of Melbourne also explores why each material might have been used and where they were sourced. Ultimately, these cultural artifacts are often composed of both inorganic and organic compounds where several different types may interact. Therefore, pigments are often layered systems that have different interactions with various parts of the electromagnetic spectrum.

Additionally, most communities, traditional owners, and curators generally prefer that analysis is non-destructive. Spectroscopic methods are often advantageous here due to the non-destructive properties of light. However, sometimes getting the object to fit in a microscope or sample holder can be challenging, or impossible in some cases, due to its size or analysis permissions. We often spend a fair amount of time pondering if studying small samples accurately reflect the whole material, especially when dealing with complex mixtures. Our experimental focus is on sampling, data analysis, and subsequent statistical analysis. Another key challenge revolves around finding suitable reference materials that effectively model cultural or archaeological materials. Ultimately, the spectroscopic data obtained often needs to be integrated into a larger study and interpreted as part of a bigger cultural or archaeological question.

You have previously adapted techniques from other fields (such as mining) for archaeological science; what is your approach to finding innovative solutions to difficult problems?
 

Our lab focuses on multidisciplinary approaches to analyze cultural materials, artifacts, and landscapes, which often provides extraordinary views into past cultures, current societal understanding, and future insights. Alongside analyzing ceramics and glass, for the past 20 years I’ve worked with cultural pigments from Australia and North and South America – primarily iron-based ochre pigments used by Indigenous people around the world. Natural mineral-based pigments are inherently complex mixtures with interesting colors and physical properties – and an ability to last for thousands of years, so they often demand innovative solutions. Over the years, our research has led to several novel methods in archaeological science. 

For example, we were the first to apply synchrotron X-ray fluorescence microscopy analysis to pigments on Indigenous Australian objects – drawing on previous work on the XFM beamline at the Australian Synchrotron on canvas painting and work in art conservation. Our current research project on Australian ochre demonstrates that we can use soil bacteria metagenomics to distinguish ochre sources, which has evolved from studies in soil forensics.

In this way, we’re not only expanding the use of current novel technology for archaeological research, but also pushing boundaries for methods and developments in their original application and in multidisciplinary areas. Innovation is key in driving these approaches – across the technology, data modeling, and spectroscopic instruments. It’s also important to have a broader view of big research questions while exploring nuances of particular research projects.

Is there anything missing from the analytical toolbox that would help the archaeology field?
 

I’ve often joked with colleagues that it would be terrific to have a magic gray box that we point at samples to give quickfire answers – similar to what is dramatized in forensic TV shows. However, we could be closer to this vision than we thought possible a few years ago. With further developments in sensor and nano technologies, we could see some exciting new applications in archaeological science.

What other big trends in spectroscopy have you got your eye on?
 

Technological advances are continuously making smaller, portable, low-power, and high-resolution instruments for successful use in remote environments – this is key to our discoveries! For instance, we’ve analyzed rock art in remote locations that are often only accessible with four-wheel drive vehicles or by helicopter. Many lab-based technologies require stability, but with adaptations from the mining industry, for instance, we have more rugged instruments to withstand transport in pelican cases to sites.

What are you currently working on? And what gets you out of bed in the morning?
 

I’m involved in several major research projects surrounding the analysis of ochre and related pigments and larger archaeological science questions. One of which is funded by the Australian Research Council entitled “Ochre Archaeomicrobiology: A New Tool for Understanding Aboriginal Exchange,” which involves working with four Aboriginal Australian community research partners to understand if the ochre characterisation “fingerprint” can change due to mixing, cultural use and environmental site changes.

Several spectroscopic methods are in use here, including XANES, XRD, and reflectance light spectroscopy, as well as metagenomic characterization of the ochre microbes. We’re in the final year of this project and expect several exciting manuscripts to be released shortly by students and project collaborators.

Another aspect of my work revolves around the analysis of Indigenous rock art – again, with traditional owner partnerships, mainly in Western Australia. These collaborations have led to portable analysis of rock art in various remote locations – applying spectroscopic technologies to probe complex and long standing pigments. 

The most exciting part of my work falls in the discovery of connections between cultural and analytical aspects of these pigments. I am expanding on this research while working on a larger program in research and education for Archaeological Science at the University of Melbourne. The vision is to expand laboratories for Australian research studies, as well as those with international reach.

What advice can you offer those who wish to follow in your footsteps?
 

Archaeological science as a field continues to grow, especially from an analytical chemist’s perspective. Students and researchers with an analytical background are well placed to work within the field. Our archaeological history is an important aspect to understanding human past, present, and future – not to mention all the exciting projects that are currently underway to keep you interested! 

There are several pathways into the field that might not follow the “traditional” academic approach, allowing students to direct their own way into the field based on their interests and career goals. With several academic programs across the world, including the University of Melbourne, offering research in archaeological science, there’s certainly something for everyone to start their analytical archaeological career.

Professor Rachel Popelka-Filcoff is Rock Art Australia Minderoo Chair in Archaeological Science, in the School of Geography, Earth and Atmospheric Sciences at The University of Melbourne, Australia