Reconstructing the proteome of ancient peoples in soils

Soils are often one of the most common archaeological artifacts, and the clay minerals contained within soils have a unique ability to tightly bind proteins, slowing or preventing their decomposition. For this reason, a fraction of proteins added to a soil during human occupation can potentially be retained for hundreds or thousands of years, serving as a “protein fingerprint” that may shed light on the diet, agricultural activities, livestock, or even human populations themselves that inhabited region.

A recent study attempts to use mass spectrometry techniques to characterize the proteinaceous matter residing in soils from excavated farmhouses of Roman origin in the present-day Netherlands. Using a novel approach termed “peptide-mass fingerprinting”, the researchers were able to uncover a suite of keratinaceous proteins commonly found in human hair and skin fragments.

Characterizing the proteins present in living tissues has been common practice in the biomedical world for at least two decades. The application of proteomics to complex environments such as soils is, by contrast, novel, and this study represents the first published attempt to use proteomics as a fingerprinting tool in an archaeological soil. I could easily see this technique becoming valuable in reconstructing the history of not just soils, but any structures or artifacts produced from clays, as clay minerals in soils are one of the key protein-binding agents. If certain protein classes in soils, for instance keratinaceous skin proteins, could be distinguished into different isoforms, or classes, based on their molecular weight, then these protein fingerprints could be related to extant proteins.Taking this one step further, different protein isoforms are often associated with genetically distinct populations of organisms. If we could begin relating ancient protein fingerprints to their extant counterparts, we might be able to indirectly trace the human genetic history of a site or an object.

Oonk et al. 2012. Soil proteomics: An assessment of its potential for archaeological site interpretation. Organic Geochemistry, 50, 57-67.

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