Animal Agents In Human Bone Modification
Animals are a significant source of modification to human remains before and after burial. Animals trample, transport, collect, and redepo-sit bones, and they chew, fracture, and consume body parts. These activities result in disarticulation of the body and the scattering and destruction of skeletal elements, and they leave a variety of marks on bone surfaces: gnawing marks, bite marks, fractures, scratches and carrying marks, and surface modification by digestive acids. Carnivores are especially destructive; dogs, coyotes, wolves, hyenas, and leopards
break open bones to get at the marrow, and they can completely consume soft trabecular regions of bone (White and Folkens, 2005:55). The scavenging behavior of canids (Haglund 1997a; Haglund et al., 1989), pigs (Berryman, 2002; Greenfield, 1988; Spennemann, 1994), rodents (Haglund, 1997b), and even polar bears (Merbs, 1997) have been studied by forensic anthropologists. The zooarchaeological literature addresses scavenging behavior in other species (e.g., bears, lions, hyenas, and wolves in Haynes, 1983) in the several decades of research papers addressing the question of hunting versus scavenging by early hominids. Carnivore damage to ungulate remains (and other prey species) at hominid fossil sites like Swartkrans in South Africa (Pickering et al., 2000) and the FLK Zinjanthropus site at Olduvai (Dominguez-Rodrigo and Barba, 2006; Selvaggio and Wilder, 2001, and many more) is studied to determine the origins and sequence of tooth marks and tool marks on animal bones, based on species-specific tooth morphology and behavior, fracture patterns, and cutmark distribution.
These methods are used in studying human remains to discern (when possible) the sequence of events in postmortem modification of bone assemblages, and to distinguish between animal and human agents of modification. Rodent gnaw marks are perhaps the most commonly observed animal-modification on Forensic Anthropology Forensic Anthropology" href="/forensic/introduction-to-forensic-anthropology.html">human bones. These marks are generally distinctive, appearing as rows of fine scratches or parallel sets of scratches. They may appear almost as beveling on crests and ridges (Fig. 3.3). Punctures in bone made by the canines or carnassials are also distinctive and leave holes on bones and scalloped or crenulated edges on bone ends (Binford, 1981:44). But some chewing marks are not so obvious. Furrows and pits (incomplete punctures) result from the bone being carried in an animal's mouth or from a tooth traveling across but not penetrating the bone (Binford, 1981; Milner and Smith, 1989). Pits and furrows may be smooth or textured depending on the morphology of the teeth involved and the "freshness" of the bone. The bone fragments in Fig. 3.4 were chewed by pigs and probably also by dogs. The striations in the bite marks (Fig. 3.4c and 3.4d) result from the topography of the pig molars (which have many accessory cusps) and the transverse motion in pig chewing (Herring, 1976). Tooth pit size depends on the size of the tooth and
- Figure 3.3 Rodent gnawing, mandible.
its function, specifically crushing, grinding, or piercing, but also on the density of the bone being chewed. Cancellous bone near the metaphyses is less resistant than cortical bone in the diaphyses and midshafts, and so larger tooth pits may be present at bone ends (Selvaggio and Wilder, 2001). Bone chewing proceeds from the softer, cancellous bone at the ends to the harder shaft of the bone, which the animal might not be strong enough to puncture, so marks on long bone shafts are more likely to be pits and furrows (Binford, 1981:46).
Systematic study of scavenging behavior by canids (dogs and coyotes) indicates a sequence of five relatively consistent stages of scavenging:
0 = soft-tissue scavenging with no removal of body parts or modification to the skeleton;
1 = destruction of the ventral thorax and removal of upper extremities, including clavicles and scapulae; 2 = complete or partial removal of lower extremities; 3 = disarticulation of all skeletal elements except vertebral column; and 4 = total disarticulation, only cranium and miscellaneous elements and fragments remaining (Haglund, 1997a:368; Haglund et al., 1989). In forensic cases these stages correspond to time interval since death starting with a few hours at stage 1 to 22 months for stage 4.
Scavenging patterns depend on the condition of the body, cause of death, and degree of disarticulation, but in general bone ends are consumed by pigs (Greenfield, 1988), and they are targeted by carnivores as well (Milner and Smith, 1989). In the Norris Farms (Illinois) skeletal assemblage, long bone ends as well as portions of flat bones were consumed by carnivores (Milner and Smith, 1989). The remains of 30 individuals in an Oneonta cemetery (dated to ca. 1300) apparently were exposed to carnivore scavengers before being buried. In this assemblage, the most frequent damage was to the ends of long bones, face, and bones in the abdominal and gluteal regions. This is very similar to the patterns of scavenging in the Crow Creek assemblage: chewing attributed to dogs, wolves, and coyotes was most frequent on the cancellous bones, which have projections (os coxae, sacra, vertebrae) and on the ends of long bones (Willey, 1990:151).
It can be difficult to distinguish between less extreme forms of animal modification on bone. Shallow scoring or gnaw marks have been interpreted as cutmarks and as simply wear from the burial substrate. Animal chewing damage may obliterate evidence of antemortem trauma (of particular importance in massacre assemblages), mortuary processing, and other biological evidence in human remains. This is another instance when familiarity with the prehistoric environment, mortuary practice, and the faunal remains recovered from an archaeological site is extremely important in the interpretation of human skeletal assemblage histories.
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