Identification of the Triticoid-type grains (Poaceae) from archaeobotanical assemblages in southwest Asia as Heteranthelium piliferum (Banks & Sol.) Hochst.

Abstract

The so-called Triticoid-type grains are known from several prehistoric sites in southwest Asia and their identification has long been unclear. They resemble the grains of wheats and researchers suggested they may represent an extinct Triticeae species, possibly closely related to wild crop progenitors. In this study we identify the Triticoid-type grains as Heteranthelium piliferum (Banks & Sol.) Hochst. and describe the key identification criteria. The identification is based on morphological analyses of modern and archaeological material from several grass species and was first achieved with well-preserved specimens from Early Neolithic Chogha Golan, Iran. We further examined the Triticoid-type grains from recently excavated samples from Early Neolithic Ganj Dareh, Iran, and archived samples from Late Chalcolithic and Late Bronze Age Tell Brak in northeast Syria, confirming their identification as H. piliferum. Based on the study of herbarium specimens at Royal Botanic Gardens Kew, London, we provide a detailed distribution map and review the species’ biology and ecological adaptations. Collected and cultivated herbarium specimens were analysed in order to understand the high phenotypic plasticity of the growth habit, its correlation with environmental variables and its relation to grain size. In order to understand the high morphological variability of the charred Triticoid-type grains from archaeological deposits, we assessed the effects of experimental carbonisation at different temperatures on grains of H. piliferum, Triticum dicoccum, T. thaoudar and Secale vavilovii. In light of the present study, we discuss the relevance of H. piliferum for reconstructing prehistoric subsistence strategies.