Performance of 2D geometric morphometric analysis in hominin taxonomy and its application to the mandibular molar sample from Lomekwi, Kenya

The Lomekwi area, situated west of Late Turkana, Kenya, has yielded numerous hominin fossil specimens, mostly isolated teeth, dated to between 3.5 to 3.2 million years ago. The isolated dental remains from Lomekwi have been tentatively attributed to Kenyanthropus platyops, whereas a number of specimens (KNM-WT 8556 and KNM-WT 16006) have been referred to as Australopithecus afarensis. However, the type specimens of K. platyops do not have sufficient dental material preserved, which does not allow the direct comparison of the isolated Lomekwi teeth to the dentition of K. platyops. In this study, 2D geometric morphometric (GM) data of the occlusal enamel surface of the crown have been used to compare the crown morphology of eleven mandibular molars from Lomekwi to specimens attributed to Au. afarensis (n=26), Au. africanus (n=35), and Au. anamensis (n=11). The current study also compared the performance of 2D GM data to traditional crown morphology measurements (cusp areas and mesiodistal and buccolingual dimensions) in classifying molars to their correct taxon by use of a canonical variate analysis (CVA), and finding differences between taxa in MANOVAs and permutational MANOVAs. The results showed that the Lomekwi sample was not exclusively linked to any of the comparative Australopithecus taxa, and exhibited some degree of morphological uniqueness. With regards to the data type comparisons, 2D GM data has been shown to be able to more accurately classify specimens to their correct taxonomic groups, and find a larger number of significant differences between taxa than traditional crown morphology measurements.