Dvodimenzionalna geometrijska morfometrija prvih gornjih molara hominina sa teritorije Srbije - taksonomska i metodološka analiza

Abstract

Primarni cilj ove studije tiče se taksonomske identifikacije fosilnih prvih gornjih molara (M1) hominina pronađenih u Srbiji, primenom metoda dvodimenzionalne (2D) geometrijske morfometrije. U prvoj (metodološkoj) fazi istraživanja ispitana je efikasnost 16 različitih pristupa (geometrijskih modela) u klasifikaciji M1 neandertalaca i anatomski modernog čoveka. Modeli su testirani na dva seta okluzalnih projekcija krunica (n = 34 i n = 64) dobijenih orijentisanjem digitalnih 3D modela u virtuelnom okruženju ili fotografisanjem fizičkih primeraka zuba. Prilikom testiranja primenjena je klasifikacija zasnovana na linearnoj diskriminantnoj analizi (LDA) sa unakrsnom validacijom (jackknifing), gde su kao varijable korišćeni setovi glavnih komponenti (PC) koji kumulativno opisuju ≥ 90% totalne varijanse. Modeli su ispitani uporedo u prostorima oblika i forme. Najefikasniji modeli (sa najvišim stopama tačnih klasifikacija) primenjeni su u narednoj fazi studije. Identifikacije fosilnih molara iz pleistocenskih slojeva pećina Pešturine (Pes-3) i Velike Balanice (BH-4 i BH-6) izvršena je primenom modela sa oznakama Komb3A i FragA, na proširenim uzorcima. Rezultati LDA klasifikacija bez izuzetka pokazuju da su svi ispitani molari pripadali neandertalcima, što potvrđuje prisustvo ove grupe drevnih hominina na teritoriji današnje Srbije tokom srednjeg i kasnog dela pleistocenske epohe. Zajedno sa drugim nalazima iz sloja 3a Velike Balanice (čija je starost procenjena na čak 369–211 hiljada godina), zub BH-4 predstavlja verovatno najraniji fosilni zapis neandertalaca na Balkanu. Upadljiva morfološka sličnost primerka BH-4 i Sima de los Huesos uzorka (starosti oko 430 hiljada godina) predstavlja indikaciju vrlo rane ekspanzije neandertalaca sa zapada ka istoku Evrope.

The primary goal of this study concerns the taxonomic identification of hominin fossil upper first molars (M1) found in Serbia, using the methods of two-dimensional (2D) geometric morphometrics. In the first (methodological) phase of the research, the efficiency of 16 different approaches (geometric models) to the classification of Neanderthal and anatomically modern human M1s was examined. The models were tested on two sets of occlusal projections of crowns (n = 34 and n = 64) obtained by orienting digital 3D models in a virtual environment or by photographing physical specimens of teeth. During the testing, a classification based on linear discriminant analysis (LDA) with cross-validation (jackknifing) was applied, where sets of principal components (PCs) were used as variables, cumulatively describing ≥ 90% of the total variance. The models were tested both in shape space and form space. The most efficient models (with the highest correct classification rates) were applied in the next phase of the study. Identifications of fossil molars from the Pleistocene strata of Pešturina (Pes-3) and Velika Balanica caves (BH-4 and BH-6) were performed using models designated Komb3A and FragA, using expanded samples. The results of LDA classifications, without exception, show that all examined molars belonged to Neanderthals, which confirms the presence of this ancient hominin group on the territory of today's Serbia during the middle and late parts of the Pleistocene epoch. Together with other finds from Layer 3a of Velika Balanica (the age of which is estimated at 369–211 ka), the BH-4 tooth is probably the earliest fossil record of Neanderthals in the Balkans. The striking morphological similarity between the BH-4 specimen and the Sima de los Huesos sample (about 430 ka old) represents an indication of a very early Neanderthal expansion from Western to Eastern Europe.