Rivers, lakes and the sea frequently host death and crime scenes. When a body is removed from a watery grave, for example due to drowning, floods, tsunamis, shipwrecks, plane crashes or murder, specialist investigative techniques are used to reconstruct what may have happened.
This discipline, known as aquatic forensics, brings together knowledge from underwater archaeology, anthropology, marine biology and marine science. But it’s still in its infancy and there’s still a lot to learn.
The investigation of a body recovered from the water is difficult enough, with so much evidence washed away (or eaten away!) and the chemistry of decomposition so profoundly affected by the water. But when only a victim’s bones or teeth are found, the mystery becomes nearly impossible to solve.
To help fill this knowledge gap, we have spent years studying archaeological bones collected from historic shipwrecks that have lain on the seabed for centuries. We are researching ways to use the recovered bones and teeth to better understand the time spent at sea and the overall journey of the mortal remains.
Our findings could one day help forensic investigations of more recent bones, such as when full or partial skeletons (human or non-human) are recovered from oceans, lakes or rivers, or simply washed up on shore.
Reconstruction of the chain of events
Studying bones and teeth helps investigators know the sex and age of the person, and potentially identify a specific individual by studying dental restorations and DNA. In the best case, a facial reconstruction will be possible. However, sometimes we can only determine if it is not a human bone, but rather an animal.
But the particular characteristics of bones and teeth and the organisms related to them can help investigators piece together the chain of events that took place after death and before recovery. This reconstruction is the subject of research on taphonomy.
Taphonomy is a scientific term coined in 1940 to describe the processes by which organic remains, such as bones and teeth, transform over time from the biosphere (the world of life) to the lithosphere (the world rocks and dust).
Our team analyzed sheep, pig and cow bones discovered in decaying wooden barrels during underwater archaeological digs of historic shipwrecks off the coast of Western Australia.
The bones and teeth in this study are part of the collections of the WA Shipwreck Museum.
They belong to the underwater archaeological sites of:
- the Bataviaa ship of the Dutch East India Company was wrecked in 1629
- the Vergulde Draeck a Dutch East India Company ship wrecked in 1656
- the Zeewijka ship of the Dutch East India Company was wrecked in 1727, and
- the Fasta Chinese-American trader was shipwrecked in 1811.
The first three were shipwrecked while sailing to Jakarta, following what was called the Route Brouwerwhile Rapid sailed from Boston to Canton (now Guangzhou).
The wrecks were located between the 1960s and 1970s – some accidentally and some after a long search – by recreational divers and underwater archaeologists. The wrecks contained many other artifacts, including stacks of silver coins.
Our research focused on bones submerged in seawater and/or surrounded by marine sediments for 169 to 347 years. Work is ongoing, but so far we have:
- identified special chemical clues or “geochemical fingerprints” of a process known as diagenesis (i.e. the changes that occur to skeletal material over time)
- reported new insights into how single-celled marine organisms called foraminifera affect dissolution spaces within submerged bone. These microorganisms, widely used for ecological and paleontological studies, can provide a wealth of information to investigators trying to determine how much time has passed since death.
- better understand how bioerosion by bacteria and colonizing animals such as barnacles affects bones underwater.
Bones can only be found in the sea after a long time if they have been contained and protected by hard structures, such as the hull of a ship or the cabin of an airplane. Otherwise, sea animals will attack them, scatter them and fragment them. Other animals will use them as shelter.
After a long stay in the remains of a wreck, bones can become locked in concretions formed by iron objects that were on board the ship. Over time, the chemical elements of bones change, with the addition of chemical elements normally absent from living bone.
The combination of everything that was added to and removed from the bones during their long underwater rest can help investigators piece together events after death.
This knowledge can be crucial in forensic investigations.
Identify old bones by scanning the collagen they contain using mass spectrometry
Quote: How Age-old Bones from Australia’s Historic Shipwrecks Can Help Us Solve Crimes (2022, February 8) Retrieved February 12, 2022 from https://phys.org/news/2022-02-centuries-old-bones- australia-historic-wrecks.html
This document is subject to copyright. Except for fair use for purposes of private study or research, no part may be reproduced without written permission. The content is provided for information only.