CH.7: Processing, Resolving Commingling, and PReserving Remains

Principles of Skeletal Processing and Preparation

• Remains often arrive in the lab with remaining soft tissue and/or other adhered material

  • Obscure skeletal remains

• Processing

Processing

• Removal of soft tissue and other materials

• Allows for “direct visual analysis of the external bone surfaces” (p.183)

• Many approaches to processing

  • Remains should be documented (notes, photography, radiography) prior to and after processing

Prior to skeletal processing

• Mechanical removal (no tools)

• Dissection and Disarticulation

Mechanical removal

• No tools

• Significant soft tissue and/or adhering materials

Dissection and Disarticulation

• Use of sharp tools

• Take care to not scrape or nick bone

Skeletal Processing

• Maceration

• Carrion beetles

• Chemical approaches

Maceration

• Soaking in water, usually at various temperatures

  • Warm water is most common

  • Addition of detergents and de-greasing agents

• Time consuming, strong odor

Carrion Beetles

• Consume soft tissue

• Time consuming, decreases risk of compromising bone

Chemical approaches

• Bleaching, significant degreasing, etc.

• Risk integrity of bone and DNA yields

Skeletal Reconstruction

• Reassembling fragmented skeletal elements to allow better analyses and interpretations

  • Trauma, postmortem damage, etc.

• Reversible methods are preferred

  • Holding fragments together, tape/putty, reversible adhesive, etc.

• Matches should not be forced

• Often a time consuming and labor-intensive process

Commingling

• The “presence of more than one body or skeleton or the intermixing of body parts from more than one individual” (p.189)

• Mass graves, mass fatalities, etc.

Resolving Commingling

• Determining the number of individuals present

• Consideration of commingling should occur with every anthropological analysis

  • Even when it may be unlikely

• Perform skeletal inventory

  • Reconstruct if necessary

• Sort present elements by element and side

• Further sorting

• Minimum Number of Individuals (MNI)

• Most Likely Number of Individuals (MLNI)

Further sorting

• Pair-matching

• Articulation

• Osteometric sorting

• Taphonomy 

• DNA analysis

• X-ray fluorescence (XRF)

• Laser-induced breakdown spectroscopy (LIBS)

• Stable isotope analysis

• Consideration of biological indicators of age and sex, pathological conditions, etc.

Minimum Number of Individuals (MNI)

• Estimated after sorting

• Count “the number of repeated elements (or portion thereof)…and then taking the highest number” (p.192)

Most Likely Number of Individuals (MLNI)

• More accurate than MNI

  • Only for cases of good preservation

• MLNI = [(L + 1)(R + 1)/(P + 1)] - 1

• R = right, L = left, and P = pairs

Pair-matching

Association of “left and right bones based on similarities in size and morphology” (p. 191). Consider density, muscle attachment morphology, epiphyseal union, etc.

Articulation

Making associations “based on the consistency of size and fit of congruent joints” (p. 191)

Osteometric Sorting

• Consistency of size within an individual

• Statistical methods

Skeletal Sampling (DNA)

• Sampling for DNA is common in medicolegal investigations

  • DNA may be recovered from skeletal remains in some cases

• A “small window or core of bone” is removed from an element

  • Then prepared for DNA analyses (not usually performed by the anthropologist)

• Anthropologists are often a part of choosing the element to sample from

Skeletal Preservation

• Skeletal remains (as evidence) must be preserved 

  • Returned to the investigative agency or funeral home after analysis

• Remains are sometimes curated for teaching and/or research

  • Donated remains (after case resolution or through donation program)

  • Must “be done with proper legal authority and following ethical principles” (p. 194)

• Long-term storage

  • Requires use of archival storage media and stored in appropriate environment (security, humidity, etc.)