Module 3.3: Postmortem Physiological Bone Change

What happens after skeletonization?

• when soft tissue has decomposed, the remains ever a state of advanced decay

• there will be changes that impact the bone

• modification and degradation of the skeleton will largely depend on the depositional environment

Define biostatinomy

pre-burial modifications affecting the organic components

Define diagenesis

post-burial modifications affecting inorganic components ending in fossilization

What are the 7 postmortem skeletal changes?

1. weathering

2. biotubation

3. burning

4. cutmarks and fractures

5. staining

6. animal damage

Explain weathering and the factors that influence weathering

decomposition of hard tissues as a response to natural agents in the immediate environment over time

• separation of the organic and inorganic components of the bone

• organic parts of lost (from drying out, decomposing, etc.)

• sun exposure

• wet/dry cycles

• freeze/thaw cycles

• bone density

• genus/species

What can weathering do to the bone?

• bleaching

• cracking

• flaking

• warping

• erosion

Explain bioturbation

disturbance of sediment by living organisms

• caused by burrowing animals like earthworms, rodents, rabbits, weasels, moles

• no direct contact

Explain plant damage

• roots searching for water and nutrients secrete acid to break up soil which can etch the surface of buried bone

• larger roots can cause articulation

• can look like cut marks

Explain burning

cremation or burning can char or burn the bone

• level of char is impacted by…

  • fleshed or de-fleshed bone

  • temperature/duration of the fire

Explain cutmarks

incisions or cuts (v-shaped or u-shaped) in cross-sections

• chopping or hacking marks

• often the result of peri- or postmortem trauma

Explain fractures in bone changes

• perimortem and postmartem trauma

• a bone broken during perimortem is hard to fracture

• a bone broken during postmortem trauma is easier to fracture

tree branch analogy

Explain staining

bone staining from soil or discolouraiton from sediments are transported via groundwater into bone pores

• staining can also occur from prolonged contact with…

  • fluids

  • leaves

  • algae

  • metal objects

Explain scavenging

consumption and associated modifications of a set of remains by animals

• can affect the rate of decomposiiton of soft tissue and postmortem bone modification

• important to know animal modification and disturbances when studying remains

  • different species will follow a pattern of succession when colonizing or scavenging remains

What is insect scavenging

• insects will be the first scavengers to arrive if present

• forensic entomologists use insect activity to estimate the PMI from soft tissue in early decomposition

factors

• seasonality

• movement of remains

• trauma

• presence of drugs

What type of flies scavenge a body? What do they do and what is the life cycle of a fly?

• blow flies, house flies, flesh flies

• deposit eggs or maggots within minutes to hours after death

• but flies don’t modify bones

• eggs → larva → pupa → adult

What is omnivore and carnivore scavenging

• scavengers will eat soft and hard tissue

• modify, disarticulate, and disperse soft and bone tissues

• caninds: wolves, cayotes, foxes, dogs

• racoons, pigs, opossus, bears, cats, crows, vultures, rodents

What is aquatic scavenging

• sharks and fish eat soft tissue like skin

• crustacean tear away muscle

• beach flies and sea lice

• mollusks

• echinoderms