Inter- and intra-observer variation in phytolith morphometry.

BACKGROUND: Archaeobotanists and palaeoecologists extensively use geometric morphometrics to identify plant opal phytoliths. Particularly when applied to assemblages of phytoliths from concentrations retrieved from closed contexts, morphometric data from archaeological phytoliths compared with similar data from reference material may allow taxonomic attribution. Observer variation is one aspect of phytolith morphometry that has received little attention but may be an important source of error, and hence cause of potential misidentification of plant remains. SCOPE: To investigate inter- and intra-observer variation in phytolith morphometry, eight researchers (observers) from different laboratories measured 50 samples each from three phytolith morphotypes, Bilobate, Bulliform flabellate and Elongate dendritic, three times, under the auspices of the International Committee for Phytolith Morphometrics (ICPM). METHODS: Data for 17 size and shape variables were collected for each phytolith by manually digitising a phytolith outline (mask) from a photograph, followed by measurement of the mask with open-source morphometric software. KEY RESULTS: Inter-observer variation ranged from 0 to 23% difference from the mean of all observers. Intra-observer variation ranged from 0 to 9% difference from the mean of individual observers per week. Inter- and intra-observer variation was generally higher among inexperienced researchers. CONCLUSIONS: Scaling errors were a major cause of variation and occurred more with less experienced researchers, which is likely related to familiarity with data collection. The results indicate that inter- and intra-observer variation can be substantially reduced by providing clear instructions for and training with the equipment, photo capturing, software, data collection and data cleaning. In this paper, the ICPM provides recommendations to minimise variation.Advances in automatic data collection may eventually reduce inter- and intra-observer variation, but until this is common practice, the ICPM recommends that phytolith morphometric analyses adhere to standardised guidelines to assure that measured phytolith variables are accurate, consistent and comparable between different researchers and laboratories.

Multidisciplinary perspectives on banana (Musa spp.) domestication.

Original multidisciplinary research hereby clarifies the complex geodomestication pathways that generated the vast range of banana cultivars (cvs). Genetic analyses identify the wild ancestors of modern-day cvs and elucidate several key stages of domestication for different cv groups. Archaeology and linguistics shed light on the historical roles of people in the movement and cultivation of bananas from New Guinea to West Africa during the Holocene. The historical reconstruction of domestication processes is essential for breeding programs seeking to diversify and improve banana cvs for the future.

Exploring mudbrick architecture and its re-use in Artaxata, Armenia, during the 1st millennium BC. A multidisciplinary study of earthen architecture in the Armenian Highlands.

Mudbrick constructions are extremely common in ancient western Asia, including the 1st millennium structures of the southern Caucasus and Armenian highlands. However, in the Caucasus the geoarchaeological study of these materials to provide insight into building practices and social structure is a topic little researched, especially when focusing on the longue durée. Artashat/Artaxata (Ararat region, Armenia) was the capital of the Armenian Kingdom of the Artaxiads, founded in the eighties of the 2nd century BC, but even before this the site was occupied in the Chalcolithic period, (ca. 5200-3500 BC), Early Iron Age (ca. 1200-900 BC) and in the Urartian period (ca. 800-600 BC) as well. All the previous occupation phases showed communities that made extensive use of earthen constructions as determined during past and recent archaeological excavations. This multidisciplinary study seeks to examine mudbrick architecture as a proxy for environmental and social interactions during the 1st millennium BC combining geoarchaeology, archaeobotany and building archaeology. We analyzed changes and continuities in architectural form and practices, alongside reconstruction of technological and social processes, to identify issues of raw material procurement, attestation of re-use, and consistency of building practices. The results of the geoarchaeological analysis of the earthen building materials used in different parts of the ancient city point to a re-use of materials over time.