'To call each thing by its right name'? Exploring the potential of geometric morphometrics to interpret the diversity of archaeobotanical wheat grains
Keywords: geometric morphometrics
agriculture
archaeobotany
biodiversity
wheat
taxonomy

This research sets out to assess the potential of geometric morphometric (GMM) outline analysis to refine taxonomy and analyse diversity among charred wheat grains preserved in archaeological deposits. An equivalent methodology is applied across three archaeological case studies, allowing for specific research questions and the parameters and effectiveness of the GMM approach to be assessed. Analysis of experimentally charred modern wheat accessions demonstrates that a combination of two-dimensional views enables taxonomic separation based on grain shape. Morphological diversity of grains is further explored as relating to a range of factors, including varietal-level distinctions, domestication status, growing conditions and crop processing.
The first case study (Paper 1) concerns the taxonomic identification and domestication status of so-called ‘new glume wheat’ (NGW) at Neolithic Çatalhöyük (Central Anatolia), summarising existing evidence for a once-widely spread crop that has almost disappeared in the present day. Results indicate that NGW grains exhibit a strong morphological resemblance to Timopheev’s wheat (Triticum timopheevii), while morphological analysis of both grain and chaff suggest that this crop underwent a gradual co-evolutionary process of domestication during the Neolithic occupation sequence. Development of the crop is interpreted in the context of diverse plant food strategies at the site which helped to offset the risk of individual resource failure.
The second case study (Paper 2) analyses ‘free-threshing’ wheat (FTW) grains from Neolithic Çatalhöyük and Kouphovouno (southern Greece), highlighting ambiguities in the early evidence for the two genetic groupings of ‘naked’ wheats. Results indicate that a tetraploid wheat resembling modern durum was cultivated at Kouphovouno, and support evidence of hexaploid wheat cultivation at Çatalhöyük. The findings build on theories of a more southerly route of tetraploid FTWs into Europe along the Mediterranean coast, with hexaploid FTW spreading through the Balkans and Carpathian basin into central Europe. Interpretation of results considers the sustainability of the regimes associated with these crops in the long term.
The third case study (Paper 3) investigates the theorised introduction of tetraploid rivet wheat into Late Anglo-Saxon agriculture. Archaeological wheat grains are examined from twelve sites in central, eastern and south-west England, accessed through the ‘FeedSax’ (Feeding Anglo-Saxon England) project. Specimens closely resembling modern rivet wheat, and particularly traditional ‘Blue Cone’ rivet, are identified at multiple sites. The introduction of rivet is contextualised within a period of acceleration and innovation in arable production, including the strategic cultivation of a broader range of crops as corresponding to local conditions. The final study (Appendix 1) addresses related concerns, reporting on experiments comparing grain shape, size and yield of the same wheat variety grown under different agricultural regimes.
Across the case studies, insights into diverse and flexible practices of cultivation in the past are interpreted in the context of contemporary concerns regarding sustainability and the loss of genetic diversity in modern wheat farming. Overall, findings indicate much potential for further exploration of morphological diversity in archaeobotanical cereal remains using GMM, a rapidly evolving field for which new archaeological applications are continuously emerging.