All bone fragments were subjected to taphonomic examination for surface modifications largely based on Lyman (1994b; 2008), which included; weathering stage, burning, abrasion/pitting, breakage pattern, surface staining, carnivore bite marks, rodent gnawing, and butchery. All of this information was recorded in order to gain an understanding of the biostratonomic and pre- and post-depositional taphonomic processes that influenced the preservation and destruction of the assemblages.
5.3.1. Weathering stage and breakage pattern
Behrensmeyer’s (1978) five-stage weathering scale was used to help determine the length of time the bones had been left on the surface exposed to the elements. The scale was slightly modified with 1 being no/little evidence of weathering (as opposed to 0 being bone that is still greasy) to 5 being extremely weathered. Differential weathering on a fragment was also recorded, such as, if one surface had a higher weathering stage than another. Behrensmeyer (1978, 153) noted that the surface of the bone that is exposed usually has a higher weathering stage than the surface with ground contact. This can help to indicate the level of post-depositional disturbance within the assemblage, as elements that have been exposed to the surface primarily on one side indicates there was minimal disturbance.
Additionally, Lyman (2008, 271, 273) notes that NISP is the unit used for quantifying weathering stage but also adds that determining whether there is a difference between unidentified fragments and NISP may be of interest. For instance, if unidentified fragments show a proportionally higher weathering stage that would suggest long-term exposure.
The general breakage pattern of the edge of the bone was noted as angular, angular and rounded, or rounded (Figure 5-3). The ‘angular’ category does not refer to fragments with recent breakage. These categories
Figure 5-3 A fragment of mammalian bone from CCN that shows relatively heavy manganese staining, rounded edges, heavy weathering, and some abrasion on both the exterior (above) and interior (below) surfaces. Specimen ID: CCN-319. Scale = 4 cm.
throughout time (Nguyen Viet 2005), some of the skeletal elements may have been transported by water from their original depositional location.
A basic category system was developed to measure the size of each fragment, for instance; 0–50 mm; 51–100 mm. This was combined with a NISP:MNE ratio to allow for a comparison of the levels of fragmentation between sites (Lyman 2008, 150–1). As Lyman (2008, 251–2) explains, the NISP:MNE ratio measures fragmentation intensity and is calculated by the ratio of anatomically incomplete specimens to the MNE of those elements. The ratio then signifies fragment size, so higher ratios suggest smaller fragments.
This allows the ranking of elements in order from the most fragmented to least, which enables comparison of specific elements between sites, such as, fragmentation intensity of deer humeri between CCN and MB (see Chapter six, 6.3.1. and Chapter seven, 7.3.1.).
Lastly, each fragment was weighed and recorded in grams.
5.3.2. Surface staining and burning
Surface staining and colour of the bone were recorded. Manganese (Mn) staining and burnt bone can be easily confused without careful examination under a microscope.
Manganese will usually adhere to the surface of the bone like a crust and is usually patchier than burning, it also does not demonstrate the fine-striated cracking or shrinkage caused by heat exposure (Figure 5-3). Manganese can form due to three main taphonomic reasons (see López-González et al. 2006, 713–4; Marín Arroyo et al. 2008).
Firstly, it may derive from the surrounding limestone bedrock or from the presence of groundwater, both of which contain minor amounts of manganese. Secondly, in a humic/
decomposing environment the degradation of organic remains into the soil produces metal-organic complexes that act as carriers of trace elements. Lastly, bacteria and fungi release manganese ions when utilising the organic part of complex molecules. Thus, it is important to attempt to distinguish between burnt bones and manganese staining as burnt bones in an archaeological context potentially implies human activity, while manganese staining is a natural geochemical process. In limestone cave environments, manganese staining on bone is probably a result of the surrounding bedrock. Conversely, CCN and MB are open-sites that contain human burials and large midden deposits, which suggests a humic soil environment is probably causing the manganese staining.
The presence of burnt bone was recorded and a differentiation was made between bones that were slightly burnt, heavily burnt, or calcined. Burnt bone is black in colour
because as the collagen is heated, the specimen becomes carbonized. Calcined bone is typically white or bluish-grey as it has been exposed to continued heating of above 600
°C, which has oxidized the carbon (Lanting et al. 2001, 250; Lyman 2008, 275). The spatial and temporal distribution and abundance of burnt bone can potentially provide information on human activity and site use, such as location of hearths or an increase in burning activity.
5.3.3. Carnivore, rodent, and anthropogenic modifications
Carnivore bite marks and rodent gnaw marks were recorded. In cases where carnivore marks were ambiguous it was noted with a question mark. Carnivore activity can leave a variety of different marks such as, tooth bites in the shape of pits, tooth scraping along the surface of the bone, and acidic marks through digestion (Fisher 1995, 36–43). Rodent teeth leave characteristic gnawing marks on bone (Klippel and Synstelien 2007). The presence of carnivore or rodent marks attests to exposure of skeletal remains long enough for scavengers to gain access to them. It also demonstrates that humans were not the only agent of modification in the assemblage.
Butchery marks were identified, recorded, and described following the conventions established by Potts and Shipman (1981) and Greenfield (1999). Cutmarks are grooves with an asymmetrical V-shaped cross-section that often contain fine, parallel striations within the groove (Potts and Shipman 1981, 557), though sharp metal knives usually produce a distinct and smooth V-shape with no or minimal striations (Greenfield 1999, 803–4). Chopmarks are produced by striking the bone surface at a roughly perpendicular angle, and often produce broader V-shapes that do not show striations (Potts and Shipman 1981, 557).
Anatomical placement was noted with the purpose of deciphering butchery methods.
For instance, placement of cutmarks could help distinguish skinning versus disarticulation of limbs. Following Rixson (1989) and Amano et al. (2013), placement of cutmarks was used to develop a chaîne optératoire of five generalised butchery practices (see Chapter six, 6.3.5, and Chapter seven, 7.3.5.). Adaption of Rixson (1989) and Amano et al. (2013) was as follows:
Primary: slaughter, skinning, and evisceration of carcass, may include removal of antlers, head, or feet.
Secondary: initial division / gross dismemberment of carcass into major portions at the joints to produce meat-yielding units, e.g. front and hind limbs
Tertiary: reduction or disarticulation to reduce major units into smaller pieces for cooking or further processing, e.g. defleshing
Fourth: Marrow exploitation
Fifth: working of bone, artefact production
Bone artefacts were given a detailed examination and analysed for use-wear and residue. Ultimately, the bone artefact analysis is not covered in this thesis as it was determined to be out of the scope for this project. Instead the artefact analysis will be undertaken in future research projects.
Bone artefacts, butchery marks, carnivore bite marks, and rodent gnaw marks were analysed under a Dinolite microscope (AM313 FUT) and images were taken using the software DinoXcope Mac version 1.9.7. Macro images were taken using a Canon EOS Rebel XSi and images were edited using the software Gimp. Some particularly important artefacts were taken to ANU for further analysis under higher microscopy including SEM analysis.