Geometric morphometric analysis of Neolithic wheat grains: insights into the early development of free-threshing forms

Abstract

Current knowledge of the origins and routes of introduction of both tetraploid and hexaploid free-threshing wheats (FTWs) from western Asia into Europe remains imprecise. Archaeobotanical distinction of ploidy level is often dependent on sparsely recovered rachis segments, while more specific identification of cultivars within ploidy groups using morphological characteristics of either grain or chaff is generally considered unreliable. This study offers a complementary approach by using geometric morphometric (GMM) analysis of grain shape to assess taxonomic and variety level distinctions in archaeobotanical FTW remains. Two substantial and well-preserved assemblages of Neolithic FTW grains from 7th millennium bce Çatalhöyük (central Anatolia, Turkey) and 6th millennium Kouphovouno (Peloponnese, Greece) were analysed with the aim of shedding light on the naked wheats cultivated by these early agricultural communities. While chaff remains from Çatalhöyük indicate a hexaploid FTW crop, no such diagnostic remains were recovered from Kouphovouno. GMM analysis of the archaeobotanical grains has corroborated early cultivation of hexaploid naked wheat at Çatalhöyük, whilst revealing that a tetraploid wheat, most closely resembling ‘unimproved’ durum wheat, was likely grown at Kouphovouno. The Kouphovouno findings are contextualised within existing theories of a Mediterranean route for introduction of tetraploid FTWs from western Asia to south-western Europe. At both sites, an assessment of the role of FTWs over time suggests changes in the cultural value attributed to these crops and/or the sustainability of the agricultural regimes they were associated with.