Determining the depositional environment and the postmortem alterations to a set
of remains are aspects of forensic investigations that are necessary to explain the
circumstances surrounding the death of the individual. Further research on the
taphonomic agents that can impact skeletal material can aid in the differentiation between
various postmortem alterations that impact a single set of remains. The present study
focuses on organic staining as a method for reconstructing the deposited environment of
the remains and the taphonomic agents in which they came into contact.
Organic staining results largely from tannins leaching from plant materials,
including wood and leaves, and therefore can be seen on bone deposited in wooden coffin
environments or on terrestrial surfaces. The present study hypothesized that the degree of
staining observed on skeletal elements would increase as the length of exposure to the
organic matter increased and that different plant materials, and environments, would
leave different patterns or colorations of staining.
The skeletal elements consisted of 150 commercially available pig (Sus scrofa)
femora that had the epiphyses removed and were completely defleshed without utilizing
chemicals or boiling. The sample was divided into three groups with differing conditions
and/or types of organic material introduced. Some were buried in a marshy environment
within wooden boxes constructed of ten wood types commonly utilized in coffin construction throughout U.S. history: hickory (Carya sp.), walnut (Juglans sp.), cherry
(Prunus sp.), soft maple (Acer sp.), mahogany (Swietenia sp.), yellow pine (Pinus sp.),
poplar (Populus sp.), cedar (Cedrus sp.), oak (Quercus sp.), and spruce (Picea sp.).
Additional femora were deposited in plastic containers lined with the same wood types as
above and filled with tap water. Five control bones were deposited in a container with
tap water and five additional bones were placed in a container with commercial tannic
acid. The final group of femora was deposited on the ground surface surrounded by four
types of dead vegetation: evergreen pine needles (Pinus strobus), northern red oak leaves
(Quercus rubra), sugar maple leaves (Acer saccharum), and acorns (Quercus rubra)
collected from the Boston area.
The bones were removed once a month from their experimental environments and
left overnight to dry. The level of staining that manifested on the osseous material was
recorded qualitatively using the Munsell Soil Color Chart under a consistent indoor 40-
watt daylight light bulb. The staining was recorded after two months upon initiation of
the study and every following month until the study’s completion. After the color
staining was recorded, the bones were returned to their experimental environments until
the next interval of data collection. An additional sample of 15 bones, which were
previously buried with direct soil contact, was also analyzed. These bones were either
buried within the O, A, or C soil horizons for an interval of 1, 2, or 3 years prior to
analysis. They were photographed and the staining was classified on one occasion after
which the bones were permanently withdrawn and not returned to the experimental
environment.
In all of the experimental environments, staining was present after two months of
exposure, and the color darkened across the bone surface with each episode of data
collection. Both groups exposed to the wood types displayed staining across the entire
bone surface with a few major colors on the bone shaft, while minor colors were only
expressed along the margins or as small patches along the shaft. As the buried boxes
began to break down, which is commonly observed in coffin burials, soil was able to
infiltrate the boxes and contact the bones. This process resulted in multiple shades of
brown to be present in the staining across bones in multiple wood types. The bones in the
plastic containers with wood exhibited a larger variation in color staining likely due to a
higher concentration of tannins restricted to a smaller area around the bones combined
with a lack of water inflow. The staining ranged from red for bones with mahogany to
brown for bones with cedar to even dark gray or black on bones with walnut and tannic
acid, respectively. The bones in plant matter differed in that the organic staining was
sporadic, often with large areas of very pale brown or yellowish brown coloration and
with smaller patches of shades of darker brown. The staining present on the buried soil
bones was intermediate to the other samples, in that it was diffuse across the shaft with a
large range of colorations present.
The results from the present study indicate that staining can manifest on bone
within a relatively short time frame once skeletonization occurs and a variety of
colorations or patterns of staining can manifest based on the plant material. The present
research demonstrates the potential of organic staining to aid in estimations of the postmortem interval as well as an environmental reconstruction through species
identification.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/23851 |
| Date | 13 July 2017 |
| Creators | Pollock, Corey Rae |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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