Faculty Mentor: Stefania Wilks (Anthropology, University of Utah)

Ground stone tools used to process small seeds, nuts, and roots are among the most common artifacts in the archaeological record. The physical act of grinding compacts starch granule residues deep within the interstitial matrix of the stone’s surface. Identifying morphological characteristics of the starch granules are used to provide direct evidence for plant taxa that were processed and consumed. Archaeologists use starch granule evidence to reconstruct the foraging patterns of people in the past and how those choices affect where they lived. The post-use contamination of buried archaeological artifacts can occur during deposition, excavation, storage, and pretreatment of the samples in the laboratory. Protocols to minimize contamination of starch residues in both enclosed lab spaces and open-air field collections have been documented in experimental studies. This project examined the potential of soil sediments to contaminate archaeological starch residues lodged deeply in the cracks and crevices of buried ground stone tools. Starch residues were sampled from 34 uncurated ground stone artifacts excavated at Connley Caves in southern Oregon. Ground stones from the archaeological site are important because they offer insight into the settlement and subsistence patterns of past humans who lived during the rapid climate and environmental transitions in the region at the end of the last glacial ice age. The results of this analysis found very few starch granules in the control (n=3) or surface residues (n=12) when compared to 82% of the archaeological residue samples (LS 1-28). However, 89% of the total starch granules observed in the surface samples (n=128) were attributed to the last six ground stone (LS 29-34). These tools were sampled in a different location and on a different day from the others. Many of the starches observed were identified as modern maize and wheat starches, all of which suggest the tools may have been exposed to contamination after they were extracted, possibly during sampling. Thus, when using starch grain analysis, it is important to collect and analyze sediments that are adjacent to artifacts so that comparisons can be made between number and type of starch granules found within the surface to those that occur on the surface of the tools themselves. This research expands our understanding of how plant starches enter and persist in archaeological sediments.

Bibliography

Dozier, C.A. (2016) Airbourne Starch Dispersal from Stone Grinding: Experimental Results and   Implications. Journal of Archaeological Science: Reports 8:112-115.

Haslam, M. (2004) The Decomposition of Starch Grains in Soil: Implications for Archaeological Residue Analysis. Journal of Archaeological Science 31: 1715-1734.

Louderback, L.A., Wilks, S., Herzog, N.M., Brown, G.H., Joyce, K., & Pavlik, B.M. (2022) Morphometric Identification of Starch Granules from Archaeological Contexts: Diagnostic Characteristics of Seven Major North American Plant Families. Frontiers in Earth Science, https://doi.org/10.3389/feart.2022.897183

Louderback, L.A., Field, J., & Janetski, J.C. (2015) Curation Practices and Extraction Methods in Relation to Starch Grain Yields from Ground Stone Artifacts. Journal of Archaeological Science: Reports 4, 535-540. https://files.acrobat.com/a/preview/39a53e24-7db5-4652-9292-e5579da09db2

Ma, Z., Zhang, C., Li, Q., Perry, L., & Yang, X. (2017) Understanding the Possible Contamination of Ancient Starch Residue by Adjacent Sediments and Modern Plants in Northern China. Sustainability 9:752-762.

Wilks, S.L., Paredes, S.A., & Louderback, L.A. (2024) Starch Granule Yields from Open-Air Metates Unaffected by Environmental Contamination. American Antiquity, 1-9. https://doi:10.1017/aaq.2023.106