A Non-Destructive Method for Distinguishing Reindeer Antler (Rangifer tarandus) from Red Deer Antler (Cervus elaphus) Using X-Ray Micro-Tomography Coupled with SVM Classifiers.

Alexandre Lefebvre,Jean-Marc Pétillon,Frédéric Santos,Gael Y Rochefort,Dominique Le Denmat,Benjamin Salmon,Luca Bondioli

doi:10.1371/journal.pone.0149658

Abstract

Over the last decade, biomedical 3D-imaging tools have gained widespread use in the analysis of prehistoric bone artefacts. While initial attempts to characterise the major categories used in osseous industry (i.e. bone, antler, and dentine/ivory) have been successful, the taxonomic determination of prehistoric artefacts remains to be investigated. The distinction between reindeer and red deer antler can be challenging, particularly in cases of anthropic and/or taphonomic modifications. In addition to the range of destructive physicochemical identification methods available (mass spectrometry, isotopic ratio, and DNA analysis), X-ray micro-tomography (micro-CT) provides convincing non-destructive 3D images and analyses. This paper presents the experimental protocol (sample scans, image processing, and statistical analysis) we have developed in order to identify modern and archaeological antler collections (from Isturitz, France). This original method is based on bone microstructure analysis combined with advanced statistical support vector machine (SVM) classifiers. A combination of six microarchitecture biomarkers (bone volume fraction, trabecular number, trabecular separation, trabecular thickness, trabecular bone pattern factor, and structure model index) were screened using micro-CT in order to characterise internal alveolar structure. Overall, reindeer alveoli presented a tighter mesh than red deer alveoli, and statistical analysis allowed us to distinguish archaeological antler by species with an accuracy of 96%, regardless of anatomical location on the antler. In conclusion, micro-CT combined with SVM classifiers proves to be a promising additional non-destructive method for antler identification, suitable for archaeological artefacts whose degree of human modification and cultural heritage or scientific value has previously made it impossible (tools, ornaments, etc.).

Highlights

Studies on the characteristics of prehistoric osseous material contribute to a better understanding of prehistoric societies and help to reconstruct the economic, technical, and symbolic interactions between human groups and the animal world [1,2,3,4]
According to the related confusion matrix (Table 5), archaeological red deer antler and reindeer antler could be distinguished with an accuracy rate of 96% using a combination of bone microarchitecture criteria
Artefacts sampled that came from peripheral antler elements were misclassified by the support vector machine (SVM) classifiers. This is the first instance to our knowledge of a non-destructive method being reported, combining micro-CT analysis and SVM classifiers to distinguish archaeological antler at a species level

Summary

Introduction

Studies on the characteristics of prehistoric osseous material contribute to a better understanding of prehistoric societies and help to reconstruct the economic, technical, and symbolic interactions between human groups and the animal world [1,2,3,4]. Among the osseous material available in the surrounding environment (i.e. bone, antler, and dentine/ivory), antler was used throughout the Upper Palaeolithic in Western Europe (40,000–11,000 years cal BP) in the manufacture of a significant proportion of hunter-gatherer equipment. The identification of these raw materials could help to indicate the acquisition strategies of particular groups, specific technical know-how, and even symbolic choices in relation to species, where both species were available in the environment

Methods

Results

Discussion

Conclusion