Alexandre Lefebvre

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.).

The exclusive use of fracturing techniques is well established in the antler industries of numerous Upper Palaeolithic cultures (Aurignacian, Gravettian, Solutrean, Badegoulian). During the Magdalenian period (21–14 ka cal. BP) antler blanks production seems to be fully dominated by the double groove procedure (DGP). However, there are indications suggesting that fracturing techniques did not completely disappear. Recent discoveries of debitage by fracturing during the Last Glacial Maximum in South-Western Europe (Solutrean, Badegoulian) have prompted us to question here the possible persistence of fracturing techniques during the Magdalenian. Based on both first-hand studies of assemblages and a survey of bibliographic sources, this initial inventory shows that nine assemblages from the northern part of the Aquitaine Basin up to Valencia, attributed to the Middle and Upper Magdalenian (19–14 ka cal. BP), yielded traces of debitage by fracturing (Bourrouilla US2007 CC—or E—and F, Isturitz I/F1, Enlène SF, Bora Gran, Cendres, Rochereil 2, Peyrazet 4-5, Murat V/Vn/VI). With generally few occurrences per assemblage, debitage by fracturing remains a limited phenomenon compared to the dominant debitage produced by grooving. Only the assemblages from Cendres and Bora Gran, located on the Mediterranean Iberian coast (the latter being the most significant for this period), do not follow this pattern. Two operational schemes have been proposed: the progressive reduction of a block by successive flake removal (Isturitz I/F1, Peyrazet 4-5 and perhaps Bora Gran) and splitting sometimes carried out on an anvil (Bora Gran, Isturitz I/F1). Despite the difficulty of incorporating these elements into a consistent techno-economic system, the few finished objects identified that were manufactured by fracturing (Isturitz I/F1, Peyrazet 4-5 and possibly Murat V/Vn/VI) provide insights into the co-occurrence of these types of debitage with the production of a minimally shaped toolkit (wedges, pressure tools). Renewed interest over the last few years in antler debitage by fracturing, which falls squarely within this session of the Société préhistorique française, sheds new light on the position of fracturing techniques which, ultimately, persist throughout the Upper Palaeolithic/Epipalaeolithic sequence in south-western Europe. The paradigm that tended to limit these practices to distinct techno-complexes no longer fits the current state of research: fracturing techniques were an integral part of thetechnical system of Palaeolithic societies for nearly 30 millennia.