Untitled

Abstract

The Lower Pleistocene locality of Dmanisi, Georgia, positioned at an important temporal and geographic junction in human evolution, has produced an abundant hominin fossil sample. The combination of derived and primitive characteristics within these hominins has provoked debate as to the evolutionary significance of Dmanisi for the early evolution of the genus Homo and the earliest dispersals of hominins outside Africa. Included within the Dmanisi hominin sample are four mandibular specimens, including one of the smallest Lower Pleistocene mandibles assigned to Homo, one of the largest assigned to Homo, and the earliest known edentulous hominin mandible. The range of variation displayed by this group of mandibles has been central to arguments regarding the taxonomic assessment of the Dmanisi remains. This paper tests the null hypothesis that variation in the Dmanisi mandibular sample is the result of sampling intraspecific variation, particularly age-related growth and skeletal size dimorphism, by using a quantitative metric approach. Utilizing both individual and nested resampling approaches, variation within the Dmanisi sample is compared to the patterns of variation seen in contemporary Homo sapiens, Pan troglodytes, and Gorilla gorilla. When individual trait comparisons are made, the results of these analyses suggest that in some metric characters the Dmanisi variation is greater than expected based on intraspecific variation in the comparative taxa. However, when the results for individual characters are considered jointly, the null hypothesis of a single hominin taxon at Dmanisi cannot be rejected. These results, alongside anatomical and geological assessments of the sample, support the hypothesis of a single Dmanisi hominin taxon. These results do raise interesting questions regarding baseline variation, including that associated with sexual dimorphism and development, in the Dmanisi hominins specifically, and early Homo erectus more broadly. INTRODUCTIONT he site of Dmanisi, located in southern Georgia, has yielded a rich assemblage of terminal Pliocene/early Pleistocene fossil hominins 1 . Excavations in 1991 yielded a hominin mandible (Gabunia and Vekua 1995) and excavations continuing to the present have uncovered well preserved cranial and post-cranial materials from multiple individuals derived from a tightly confined stratigraphic context (Ferring et al. 2011;Gabunia et al. 1999;Gabunia et al. 2000;Gabunia et al. 2002;Lordkipanidze et al. 2006;Lordkipanidze et al. 2007;Rightmire et al. 2008;Vekua et al. 2002). The fossil assemblage is placed at an important junction, both geographically and temporally, for understandings of the evolution of early Homo and the emergence of Homo erectus (Wood 2011). Included in the hominin sample from Dmanisi are four mandibles encompassing a large range of anatomical and metric variation. The variation within the mandibles has generated considerable discussion as to the proper interpretation of the Dmanisi hominins and the broader significance of the site fo...