Spatial approaches to site formation and carnivore-hominin interaction at Dmanisi, Georgia

Abstract

Spatial analyses are valuable tools for examining abiotic and biotic site formation processes that contribute to the accumulation of archaeological and paleontological material. When these analyses are used in tandem with taphonomic and geologic interpretations, archaeologists can make stronger arguments for site reconstruction and behavioral inferences. Spatial analyses have been used for decades to understand how human behaviors and the deposition of material are linked. Similarly, spatial behaviors by carnivores are apparent, with some species, namely hyenas, differentially using space for various behaviors. Through the lens of spatial analysis, this dissertation examines the degree to which abiotic and biotic agents contributed to site formation at the Early Homo site of Dmanisi, Georgia. Taphonomic and geologic studies at Dmanisi have interpreted the hominin-bearing deposits in Block 2 as resulting primarily from biotic agents, mainly carnivores, and not from fluvial or colluvial action (Lordkipanidze et al., 2006, 2007; Tappen et al., 2007). This dissertation expands on these interpretations by providing spatial evidence from two excavation areas (M6 and Block 2) and multiple strata used in conjunction with taphonomic analyses by Martha Tappen and geologic and archaeological analyses by Reid Ferring to compare relatively horizontal strata to the complex pipe/gully fill strata in which the highest concentration of bones are found. Orientation and dip, fragmentation and winnowing, and skeletal refits are examined and the results for each support the interpretation that the assemblages are not a product of fluvial and colluvial deposition. What is more, an analysis of spatial patterning indicates that higher densities of carnivores are located in the pipe/gully fill deposits than elsewhere. Also, coprolites are prevalent in these deposits, but follow a different spatial distribution than the skeletal material. Taphonomic analyses demonstrate that carnivores contributed greatly to the consumption of carcasses, and several species of carnivores are present at Dmanisi during this time. Each species of hyena has been observed to defecate in specific areas, both inside of the dens and outside in latrines, which could explain the cluster of coprolites in the B1 strata in Block 2. Two of the pipe/gully fill phases of B1 (B1x and B1y) are within a complex basalt formation that could have provided a secluded area for carnivores to consume carcasses and potentially have dens. These coprolites provide potential insight into carnivore space use in the Early Pleistocene, but further analysis is necessary to attribute the coprolites to specific animals. In any case, carnivores appear to be the main influence on site formation at Dmanisi, while the hominin imprint is minimal. In order to understand the potential carnivore-hominin interaction and the timing of carcass access at Dmanisi, this dissertation also provides new analytical methodology for studying bone fracture angles produced during the marrow acquisition process. In lieu of agent-specific surface modifications (i.e. carnivore tooth marks or hammerstone percussion marks), green breaks on long bones are difficult to attribute to a specific agent of breakage. By quantifying fracture angles, perhaps archaeologists can infer the causal agent of breakage and interpret the influence of carnivores and hominins on bone breakage. This dissertation contributes the results of a controlled breakage experiment where bones were broken by hyenas and hammerstones. Based on the results of the fracture angle analysis, different long bones create different fracture angle assemblages and it is necessary to identify the long bone fragments to at least limb portion (upper, middle, lower) if not to skeletal element. In addition, the preliminary results of the hyena created assemblage shows that hyena broken bones result in fracture angles further from 90° than hammerstone broken bones. Carnivores played an important role in the accumulation of faunal material at Dmanisi, Georgia. Evidence for abiotic site formation processes, such as fluvial and colluvial deposition, is minimal and likely did not affect the original depositional context of the stones and faunal material. The hominin contribution to site formation is also minimal, but perhaps understanding fracture angles created during the marrow acquisition process can allow for further testing of this hypothesis in the context of Early Homo. By examining these different factors, this dissertation broadens the knowledge of how carnivores and hominins contributed to site formation during the earliest expansion of our genus outside of Africa.