Detection of early postmortemchanges in burnt bones through

histotaphonomical analysisEMESE VEGH, ANDREA CZERMAK, NICHOLAS MARQUEZ-GRANT, RICK SCHULTING

American Association of Physical Anthropologists Annual Meeting 2020, Los AngelesSession: Forensic Anthropology: Methods and Approaches

OVERVIEW

1. Background1.1 Bone Histology

1.2 Diagenesis

1.3 Burning

2. Research Question & Rationale

4. Experimental Outline

5. Methods

6. Results & Discussion

7. Conclusions

BACKGROUND: BONE HISTOLOGY

BACKGROUND: BONE DIAGENESIS3 distinct pathways of diagenesis (Collins et al. 2002):

◦ 1. Chemical degradation of the organic component (collagen hydrolysis)

◦ 2. Chemical degradation of the inorganic phase (bioapatite dissolution)

◦ 3. Microbial degradation of both the inorganic and organic phases

Microbial bioerosion: specific causative agents yet to be identified

CYANOBACTERIAL TUNNELLING

BUDDED MFD

WEDL TUNNELLING

LINEAR LONGITUDINAL MFD

LAMELLATE MFD

WEDL 2

Brönnimann et al. 2018, 46, Fig. 4

BACKGROUND: BURNING

2 important factors:Heating temperatureDuration of fire

Macroscopic changes:WarpingFragmentationColour changeShrinkage

BACKGROUND: BURNT BONE MICROSTRUCTURE

-Relatively few studies: - fire temperature and duration

- species identification

- age-at-death identification

- No major histomorphological changes reported under:- 600°C (Bradtmiller and Buikstra, 1984),

- 700°C (Herrmann, 1977),

- 900°C (Squires et al., 2011),

- or 1200°C (Cattaneo et al., 1999)

RESEARCH QUESTION & RATIONALE

Can we learn if bones were fresh or decomposed when burnt from microbial bioerosion signatures?

◦ Hypothesis: Microbial bioerosion survives cremation, indicating biological degradation of bone prior to cremation.

◦ Implications in forensic anthropology and funerary practices in archaeology

◦ Few cases in the forensic anthropological literature

EXPERIMENTAL OUTLINE

PMI: 14, 31, 91, 180, and 365 days

METHODS1. Optical transmission microscopy

2. Backscattered electron microscopy (BSEM) on the electron microprobe

Bones degreased (MeOH/Chloro mix) for up to 20 weeks

Embedded in epoxyresin

~50-70μm thin-sections cut with a diamond saw

Fixed onto glass slides

Transmission light microscopy (x50, x100, x200, x400 magnification)

Data labeller application built using Python (Flask web framework) and Javascript (jQuery) programming languages.

METHODS

2. BSEM

Resin block ground & polished

Carbon-coated

Compositional images taken

Turner-Walker, 2019

METHODS: Data labelling application 100 equal sized image

Only 50x images used

N=27,000

Blocks picked at random across all images to exclude bias

- Feature present = ‘TRUE’ in database automatically created by the application

- The cumulative score for the 100 blocks present a % score for each image.

Bronnimann et al. 2018

All labelled as cyanobacterial tunnelling.

Labelled as cyanobacterial tunnelling in Brönnimann et al. 2018, 46, Fig. 4

RESULTS

Budded MFD -- WSF5D6M3_unburnt Lamellate MFD-- SWF5D1Y1_burnt

Feature r

unburnt

p

unburnt

r

burnt

p

burnt

Wedl tunnelling 0.442 0.00009** -0.016 0.886

Wedl 2 0.170 0.151 0.254 0.012**

Cyanobacterial

tunnelling

-0.204 0.084 0.114 0.312

Lamellate mfd 0.493 0.00001** 0.091 0.412

Budded mfd 0.531 0.000001** 0.296 0.006**

Crack 0.064 0.591 0.184 0.095

Hairline crack 0.278 0.017** 0.159 0.150

Linear regression: H0= Presence (in %) of X feature per bone does not increase with postmortem time period.** shows significant p-values.

RESULTS: BSEM- Hypermineralised areas present around cracks and enlarged canaliculi

- These don’t look similar to BSEM images of tunnelling in Turner-Walker 2019

- These contrast differences were obliterated by the burning process.

WSF5D1M3_unburnt WSF3D3M3_unburnt WSF5D6M1_burnt

- Fresh burnt bones: Wedl tunnelling, Wedl 2, and cyanobacterial tunnelling present → can be caused by burning → not areliable indication of bioerosion- Wedl tunnelling, budded and lamellate MFDs had a statistically significant relationship with time since deposition.

Only budded MFD was significant after burning, but high coefficient of variation (CV).

Cracks and hairline cracks: more associated with burningCracks: increase in their presence with time since deposition on burnt bonesUnreliable features – can be caused by preparation

DISCUSSION

Connecting Wedl 2 -WSF5D6M5_burnt

Wedl 2 – Freshly burnt bone (SWF1FR2_burnt)

Wedl 2 --WSF5D6M3_unburnt

CONCLUSION1. First histotaphonomic research to apply quantitative analysis ofmicrobial bioerosion features.

2. Most microbial bioerosion features on bones are not reliableindicators of putrefaction/decomposition in unburnt or burntbones.

3. Budded MFD might be used as a proxy for decomposition, butmore research is needed.

4. Cyanobacterial tunnelling are most probably Volkmann’s canalsthat survive intense cremation.

5. BSEM is not a useful technique in microbial bioerosion researchin burnt bones.

Thank you for the attention!Acknowledgments:

- Supervision

Rick Schulting, Nicholas Marquez-Grant

- Research, Analytical & Data Analysis

Andrea Czermak, Kevin Lemagnen, Victoria Smith, Robert Hedges

- Fire

Tansy Branscombe, Katelyn Farrants, Gary Hung, Kevin Crawford, JoeGraystone

- Funding

Meyerstein Fund, Wolfson College, School of Archaeology Award, SidneyPerry Foundation, Stapley Trust