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  Taphonomic Analysis

Taphonomy is, in general terms; a study of the postmortem, pre-burial, and post-burial histories of faunal remains (Lyman 1994). Taphonomic analysis attempts to reconstruct the chronology of a variety of postmortem processes that have produced a faunal assemblage or a subset of the assemblage. Many of these processes leave signatures on the surface of bone which, if properly identified, are a powerful method of assessing everything form natural and cultural formation processes to complex cultural rituals.

Weathering & Root Etching

The slow decomposition of bone results in a somewhat predictable alteration of the bone surface. Cracking of the surface, parallel to fiber structure, results in surface exfoliation. The loss of the outermost surface causes the bone to have a fibrous appearance, which increases in coarseness with increased exposure until the bone loses integrity (Behrensmeyer 1978). In areas of root activity, chemicals secreted by roots etch the bone surface and accelerate this weathering process. Bone that remains unburied for extended periods of time can also become bleached white by the sun. This bleaching also accelerates the weathering process of a bone.

Carnivore & Rodent Tooth Marks

Unburied and near surface bone is often subject to alteration by scavenging carnivores. In their attempts to remove meat from the bone, and even transport the bone itself, carnivore teeth leave characteristic markings on the bone surface which can often be identified with the naked eye or minor magnification. While carnivores tend to prefer fresh bone for flesh and marrow procurement, rodents tend to gnaw at dry bone to obtain minerals and to sharpen and shorten their ever-growing incisors. Rodent gnawing leaves a predictable pattern of markings on a bone surface, which are easily identified by the naked eye. Documentation of carnivore and rodent modification of bone reveals important information regarding disposal practices as well as environmental conditions.

Burned & Calcined Bones

When in contact with heat or fire for a relatively short duration of time, bone becomes charred or blackened. Bone that is in contact with heat for long periods of time or is repeatedly heated and cooled attains the white appearance of calcined bone. The effect of burning on the resiliency of bone varies with animal class, skeletal element, and intensity of the burning. Documentation of burned & calcined bone signatures allows for analysis of cooking and disposal practices.

Butchery Analysis

In addition to the size and shape of faunal remains allowing for identification of those cuts of meat obtained from a carcass, taphonomic analysis provides information regarding the types of tools used to obtain these cuts. Sawed, chopped, and fractured bones retain signatures of skinning, evisceration, disarticulation, and marrow extraction. For a complete butchery analysis, the location and description of each cut mark should be documented. The results of butchery analysis allow for a variety of cultural and economic analyses to proceed.

Other Taphonomic Indicators

A variety of additional taphonomic indicators can be used to obtain a more complete understanding of a faunal assemblage and its creation. For example, small animals are particularly sensitive to climatic variation and therefore their presence absence can be used to assess seasonality, temporal shifts, and changes in hunting ranges to name a few. Another important taphonomic indicator is the association of skeletal elements and animal classes, which can reveal redeposition events. Related artifact and ecofact analysis as well as a study of the changes in soil microstratigraphy within a feature can reveal the sequence of depositional events that have occurred.

As archaeological excavation is part of the taphonomic history of an assemblage, the effects of excavation and recovery are an integral part of taphonomic analysis. Surface marks and breaks that occur during and after excavation are easily identified. Together with an assessment of the recovery techniques used, (screen aperture size, excavation tools used, etc.) an analysis of the excavations impact on the representativeness of the assemblage can proceed. For example, an excavation that utilizes 3/8" aperture to screen soil should not expect to recover the remains of small animals.

   Importance of Taphonomy

The taphonomic history of faunal material includes an analysis of all those processes that ocurred between the animal’s death and the archaeological analysis of its remains.

There are 7 commonly recognized taphonomic processes that serve to bias faunal assemblages in particular and archaeological assemblages in general.
Five of these biasing factors occur prior to archaeological excavation and include the characeristics of habitat, population density, cause of death, butchery, burial environment, and differential decomposition.

Two of the most ignored taphonomic processes are the actual archaeological excavation and subsequent analysis. A complete faunal and taphonomic analysis ensures that your research conclusions are not a result of your research design.

   Taphonomic Processes

Biotic & Cultural – species availability
- Habitat & ecological niche
- Population density

Thanatic – mechanisms of death
- Cause & location of death
- Hunting & agricultural practices
- Mortality profiles

Perthotaxic – pre-burial removal
-Butchery & cooking practices
- Differential transport & destruction

Taphic – post-burial modification
- Burial environment
- Animal and root modifications
- Differential diagenesis

Anataxic – re-exposure of buried bone
- Erosion
- Excavation

Sullegic – excavation bias
- Data recovery methods
- Excavator experience
- Bone breakage

Trephic – analysis & curation bias
- Analyst experience
- Identifiability of elements.

   Taphonomic Indicators

- Fracture patterns
- Weathering stages
- Abrasion
- Color & burning
- Root etching
- Gnaw & tooth marks
- Excavator marks
- Butchery marks
- Use wear

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