Mixing lasers and archaeology to tell stories with stones
What can rocks tell us about the history of our landscapes and people who live on them? Rhy McMillan, who recently defended his PhD dissertation in Geological Sciences, blends geochemistry and archeology in his quest to provide Indigenous communities with scientific data that provide additional support for their oral histories.
“Ancient humans interacted with so many different parts of the world around them in many different ways, and we expect folks from one particular discipline to be able to unravel all of that from the physical remnants that they left behind?" McMillan explains. ”That's a tall task!”
Most places within British Columbia are unceded territories. The Indigenous peoples within them are working to document their continuity and use of landscapes both today and in antiquity. This includes the acquisition of resources, like raw materials to make stone tools. McMillan and his colleagues at UBC’s Pacific Centre for Isotopic and Geochemical Research and the Indigenous / Science Research Cluster are applying techniques from geochemistry to archeology to identify where stone was likely collected before it was shaped into belongings. By re-analyzing existing museum collections, they can build scientific data to support histories of where ancient people likely went in the past without further disturbing archeological sites.
Older approaches linking belongings to their potential origins relied on simpler geochemical techniques with limited capacity to uniquely identify rock characteristics. McMillan likens it to describing someone by hair colour alone. “That is not really enough to narrow down an individual beyond reasonable doubt.” he says. "I'm finding out where they're not from."
Instead, McMillan uses a series of techniques including spectroscopy and laser ablation for more extensive geochemical analysis that can provide multiple independent lines of evidence while minimizing damage. "It’s less about proving where a specific belonging is from so much as systematically disproving its links to all the possible quarries and resource-gathering locations until only one remains,” he says.
With this community-driven collaborative approach to provide extensive scientific analysis, McMillan is able to document the ancient movement of stone belongings. While his dissertation focused on belongings made from obsidian, he’s hopeful about expanding the approach to more geologically-ambiguous materials in the future.
McMillan, R., Amini, M., Weis, D. (2019). Splitting Obsidian: Assessing a multiproxy approach for sourcing obsidian artifacts in British Columbia. Journal of Archaeological Science: Reports 28, 102040.