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