Skeletal taphonomy of Sus scrofa within a burial environment in the South African Highveld

Abstract

Taphonomy is the study of the environmental effects on the remains after body deposition to the time of recovery. It has become an important component in forensic investigations as it enables forensic anthropologists to estimate the postmortem interval and reconstruct the events leading up to and after death. This study focused on the skeletal taphonomy of buried remains after six years of internment to establish, if any, the relationships between the soil composition (pH and organic content) and burial environment (depth and grave positioning) with any taphonomic alterations observed on the bone.

The study was conducted at the Miertjie le Roux experimental farm located in the interior Highveld of Gauteng. The sample was made up of 39 pigs that had been buried six years prior as part of a previous study. The remains were excavated using standard archaeological techniques. Six taphonomic alterations were observed and scored, including depositional staining, adipocere formation, weathering, acidic soil corrosion, plant activity, and animal activity. Soil samples were taken from three separate levels in each grave (10 cm, at the level of the carcass and 10 cm below the carcass). Each soil sample was then analyzed for pH and the percent organic content.

The most common type of taphonomic alterations was depositional staining, followed by weathering, and plant activity, as these were observed on all the skeletal remains. Adipocere was also frequently observed as it was on 36 of the 39 skeletons. Animal activity was the least observed as it was only present on four pigs. There were significant correlations between the taphonomic relationships which included the skeletal completeness with depositional staining, adipocere formation, weathering, and plant activity. There were also significant relationships between depositional staining and acidic soil corrosion, adipocere formation and plant activity as well as weathering and acidic soil corrosion and weathering and plant activity. There were significant correlations between the soil composition and the taphonomic alterations which included pH with the skeletal completeness, depositional staining, adipocere formation and weathering and organic content with adipocere formation and weathering. The correlations with the taphonomic alterations and the burial environment included the depth with adipocere formation and weathering as well as the grave positioning with depositional staining, adipocere formation and plant activity.

Skeletal preservation was low due to the absence of many small bones. It was however increased by the presence of adipocere. The two most common colours were dark brown and brown. Dark staining was correlated with a more complete skeleton. The right side of the skeletons were the most darkly stained as they were in close contact with the cadaver decomposition island (CDI). In addition, the right sides had more adipocere formation than the left. The presence of adipocere also increased the plant activity which suggests the graves retained water for adipocere formation and plant growth. Results from the soil analyses indicated that in general the presence of the cadaver lowered the pH of the burial environment and increased the percentage organic content when compared to the controls. There was also a significant difference observed between the surface level pH and organic content compared to the soil at the level of the carcass due to the presence of the decomposing carcass. A basic pH was associated with a more complete skeleton and an increase in adipocere formation. Adipocere formation also increased by the depth of the grave. Additionally, less adipocere formation, plant activity and dark staining remains were associated with graves at the top of a naturally occurring slope.

This study confirms that there are relationships between the soil composition and burial environment with the taphonomic alterations. The soils in this study seemed to retain water and thus formed adipocere and preserved the remains especially on the right side. This further establishes that the micro-environment of the grave is important factor influencing the macroscopic appearance of skeletal remains.