Implementation of geometric morphometry in the study of shapes of Bronze Age sickles from the Volga-Ural region

Abstract

This article aims at evaluating the potential of geometric morphometry by means of an example of analysis of shapes of the Bronze Age sickles from the Volga-Ural region, as compared with the traditional morphometric approach. For the study, cast bronze sickles with hooks, categorized by V.A. Dergachev and V.S. Bochkarev into the Ibrakaevo, Derbeden, Perelyub and Yavlenka types using the traditional morphometric approach, have been selected. The analysis was applied to only full drawings of the items, including reconstructed ones, while fragmented items were not considered. The sample constitutes 167 objects: 86 Ibrakaevo, 49 Derbeden, 24 Perelyub, and 8 of the Yavlenka type. Application of geometric morphometry tools shows that, within the sample, three main forms can be easily identified, with the exception of the sickles earlier attributed to the Yavlenka type, probably due to their small number. Preparation of primary files for recording landmark coordinates and processing of files with recorded coordinates were carried out in the tpsUtil program. The analysis of characteristics of changes of the forms was carried out using the principal component method in the MorphoJ program. Summarizing the obtained results, we can say that the principal components method has been able to identify three main variations of the objects. Most clear are the differences between the Ibrakaevo and Derbeden types, which show virtually no overlap. An intermediate position between them is taken by the Perelyub type, which is also distinctively grouped in the graph being close to the Ibrakaev group. In terms of identifying individual types, the results of the study are rather consistent with the data obtained by the traditional morphometry. At the same time, it is possible to trace the vectors of shape variability for all types of tools based on three main components. Overall, it can be concluded that the method of geometric morphometry demonstrates its efficiency for the analysis of shapes of metal sickles and in future it could be applied to wider sample groups.

Keywords

• bronze age
• volga-urals
• sickles
• geometric morphometry
• landmarks
• principle components methods