New criteria for the molecular identification of cereal grains associated with archaeological artefacts

Abstract

The domestication and transmission of cereals is one of the most fundamental components of early farming, but direct evidence of their use in early culinary practices and economies has remained frustratingly elusive. Using analysis of a well-preserved Early Bronze Age wooden container from Switzerland, we propose novel criteria for the identification of cereal residues. Using gas chromatography mass spectrometry (GC-MS), we identified compounds typically associated with plant products, including a series of phenolic lipids (alkylresorcinols) found only at appreciable concentration in wheat and rye bran. The value of these lipids as cereal grain biomarkers were independently corroborated by the presence of macrobotanical remains embedded in the deposit, and wheat and rye endosperm peptides extracted from residue. These findings demonstrate the utility of a lipid-based biomarker for wheat and rye bran and offer a methodological template for future investigations of wider range of archaeological contexts. Alkylresorcinols provide a new tool for residue analysis which can help explore the spread and exploitation of cereal grains, a fundamental component of the advent and spread of farming.

A guide to ancient protein studies

“…A number of protocols have been reported for the extraction of ancient proteins, particularly for the extraction of bone protein [81][82][83] , and include protocols based on SDS buffers and polyacrylamide gels ( 24,84 ), Filter-Aided Sample Preparation (FASP) 1,85,86 , and Gel-Aided Sample Preparation (GASP) 87,88 . However, the efficacy of these protocols, their downstream effect on protein identification and resulting chemically-induced modification have not been systematically compared in studies of ancient proteins, although examples exist that compare their performance on modern material 89,90 .…”

“…Combining proteomic approaches with other biomolecular techniques, where possible, is encouraged, as multiple approaches can be used to supplement or support novel proteomic findings. For example, ancient mtDNA sequences have been used to support palaeoproteomic analyses of hominin taxonomy 7 , lipid and proteomic approaches have been used in combination to detect early Bronze Age cereal grains 88 , and proteomic and isotopic approaches have been used together to identify ancient milk consumption 12 .…”

Ancient proteins from ceramic vessels at Çatalhöyük West reveal the hidden cuisine of early farmers

“…In addition, the resolution of lipid analysis can be diminished by the mixing of different food products and the reuse of vessels 9 . Moreover, whilst fat-rich animal products are often readily identifiable 10 , there have been only a few reports of the identification of plant lipids in prehistoric pottery 11 – 13 , potentially skewing our interpretation of past resource use and culinary practice. As a consequence, our narratives regarding the development and use of early pottery in Southwest Asia and Europe have been tightly bound to wider debates concerning domestication, animal management and secondary product exploitation.…”

“…This approach has been successfully used to investigate food and other proteins trapped in calcified dental plaque, also known as dental calculus 19 , 20 . However, the application of shotgun proteomics to archaeological artefacts has so far been limited to exceptionally well-preserved examples from waterlogged 21 , cold 11 , 22 or arid contexts 23 . Beyond such exceptional contexts, it has not been clear whether dietary proteins would survive following long-term exposure to the burial environment 24 , whether sampling and extraction strategies could be made more effective at recovering food proteins from vessel walls 25 , or whether dietary proteins would survive food preparation, particularly protracted heating.…”

First lipid residue analysis of Early Neolithic pottery from Swifterbant (the Netherlands, ca. 4300–4000 BC)

“…Given the evidence of the use of the emmer in the foodcrusts from S3 vessels, the absence of plant biomarkers in our results may come as a surprise. As plant foods have low lipid content, they may be overprinted by other animal fats and may therefore be very difficult to detect through lipid residue analysis (Colonese et al 2017;Hammann and Cramp 2018). This opens up a new discussion on whether Swifterbant vessels are used for mixing freshwater fish and plant food sources.…”