ANTH Chapter 5: Forensic Taphonomy

Taphonomy Overview

• Definition: Study of the processes that affect remains after death.

• Sampling Bias: Recognition that not all remains will be preserved equally; can skew analysis.

• Differential Preservation: Some skeletal types or parts may preserve better depending on various factors.

• Importance: Essential for interpreting skeletal analyses, including perimortem trauma (injuries around the time of death) and pseudopathology (false disease indicators due to preservation conditions).

Key Concepts

• Postmortem Interval (PMI): Time since death; can be forensically or historically significant.

• Experimental Taphonomy: Investigated in settings like the "Body Farm," where decomposition is studied under various environmental conditions.

Decomposition Process

1. Algor Mortis:

   • Definition: Cooling of the body after death.

   • Rate: Approximately 1 degree/hour for the first 12 hours.

2. Livor Mortis:

   • Definition: Pooling of blood due to gravity.

   • Timing: Begins 30 minutes to 4 hours after death; becomes pronounced at 12 hours.

   • Coagulation Stage:

     • Prior to livor fixation, if the body is moved, the blood will start to pool closest to the ground.

     • After the livor is fixed, the blood coagulates and will not re-pool.

3. Rigor Mortis:

   • Definition: Stiffening of muscles due to the binding of muscle fibers.

   • Timing: Begins a few hours post-death, peaks around 12 hours, lasts 1-2 days.

Decomposition Mechanisms

Many environmental factors including temperature, moisture, and soil chemistry can affect decomposition, but there are two processes of chemical breakdown

1. Autolysis: Self-digestion of cells by enzymes.

2. Putrefaction: Microbial breakdown leading to

   • Color changes

   • Marbling (darkened veins)

   • Bloat

   • Skin slippage

Artifactual Preservation

• Definition: Methods that prevent or delay decomposition.

• Natural and Chemical factors:

  • Environment and burial substrate can significantly influence preservation.

  • Embalming: Use of chemicals to preserve remains.

  • Mummification: Natural drying of remains, often found in arid conditions.

• Saponification: Formation of adipocere (grave wax), typically in wet environments.

• Differential decomposition: Varying or disproportionate rate of decay in different body regions

  • Open wound

  • Local bacterial infection

  • Exposure to physical/chemical agents

Environmental Factors Affecting Preservation

• Warm, Dry Conditions: Favor mummification processes.

• Cool, Wet Conditions: Lead to formation of adipocere and excellent preservation in anaerobic (absence of oxygen) environments like peat bogs.

Postmortem Skeletal Changes

• Diagenesis:

  • Definition: Changes to bone due to chemical, physical, or biological processes.

  • Examples: Groundwater composition, soil pH can affect bone color and structure.

• Weathering: Degradation of bone by natural weather conditions (e.g., exposure to sunlight, freeze-thaw cycles).

Scavenging Effects on Remains

• Role of Scavengers: Insects, carnivores, and rodents contribute to decomposition understanding.

• Can help recovery efforts

• Helps distinguish non-human modification

• Types of Evidence:

  • Carnivores:

    • Create punctures and other distinctive marks with their sharp and pointed dentition.

      • Pits, punctures, furrows, scoring

    • Missing bones indicate carnivores

  • Omnivores:

    • Similar signs as carnivores but can leave different patterns.

  • Birds of Prey:

    • Marks typically found on eye orbits and facial bones

  • Rodents:

    • Provide minimal marks on bones

    • Distinct incisor marks

  • Insects:

    • Can be used to determine time since death, season, drug or poison presence, and geographic origin

Disarticulation Patterns

• Factors: Decomposition and scavenging can lead to significant disarticulation and displacement of bones.

• Environmental Movement: Gravity and water currents can transport remains, leading to observable movement in grave contexts.

Determining Time Since Death (Postmortem Interval)

• Importance: Helps narrow down identification related to the circumstances of death.

• Variability Factors:

  • Temperature: Accounts for 80% of PMI variability.

  • Body weight, humidity, and soil pH also affect decomposition rates.

• Scoring Systems:

  • Quantitative measures of decomposition: e.g., discoloration, bloating, soft tissue loss.

  • Total Body Score (TBS): Used in calculating Accumulated Degree Days (ADD), based on local average daily temperatures.

Plant Interaction with Decomposition

• Initial Effects: Plants are typically damaged by fatty acids released during decomposition.

• Recovery Processes: They can later contribute biochemically to how remains are preserved, aiding in burial location identification.

• Analytical Techniques: Tree rings and pollen analysis are effective in determining burial sites.

Aquatic vs. Terrestrial Decomposition

• Difference in Rates: Aquatic decomposition generally occurs at half the rate of decomposition on land due to cooler water temperatures.

• Chemistry Influence: Influenced by water conditions (stagnant vs. moving water) and salinity levels.

  • Decomposition occurs more rapidly in stagnant water than running water and in freshwater than in salt water.

• Algal growth rate: Strong correlation with time since submersion.

Funerary Practices

• Modern Practices: Include embalming and the use of varied coffin materials (wood, metal, concrete).

• Artificial Implants: Structures added for preservation or aesthetic purposes by funerary directors, further influencing taphonomic characteristics of remains.