Tracing microfossil residues of cereal processing in the archaeobotanical record: an experimental approach

Interdisciplinary methodological approaches are fundamental for studying tool use and crop processing patterns in the archaeological record. Many archaeological studies of plant microfossil evidence, primarily those of phytoliths, starch grains and pollen, are concerned with processing methods which can be replicated through experimentally produced plant residues. However, most of these studies rely on crop identification through the presence or absence of such microfossils while giving little or hardly any weight to taphonomy and formation processes, which are critical for interpreting archaeological contexts. An investigation of experimentally produced phytolith and pollen assemblages provides the opportunity to evaluate the impact of cereal processing on both microfossils. Controlled experiments were conducted at the Museum of Menorca, Balearic Islands, Spain, for assessing microfossil taphonomy using Iron Age Talayotic tools and Hordeum vulgare (hulled barley) grown nowadays on the island. For dehusking, a sandstone mortar and a wooden pestle were used outdoors, whereas grinding took place indoors using a limestone quern and handstone. The results indicate that the size of multicellular or anatomically connected phytoliths decreases as a result of mechanical degradation suffered through processing activities, whereas the proportion of cereal pollen grains increases through these processes. Additionally, experimental samples from dehusking and sieving provided abundant evidence of floral bracts, and also of other plant parts and even different plant species, such as phytoliths from leaves and stems and non cereal pollen taxa, which were also to be found on the surfaces of the ground stone tools. These findings highlight the importance of integrating different lines of microfossil evidence and taking into account formation and taphonomic aspects, as well as the value of experimentally produced data for a better understanding of tool use and crop processing