In a cold case that is closer to icy than chilly, scientists at the University of Southampton, have expanded the forensic toolkit to correctly identify drowning as the cause of death of a Neolithic fisherman buried in a mass grave in Chile about 5,000 years ago.
Modern forensics can confirm drowning as the cause of death in recent victims by testing for diatoms—the most common form of plankton—inside the bones of victims. However, until now, the test had never been used to determine drowning in saltwater on prehistoric human remains.
“Mass burials have often been necessary after natural disasters such as tsunamis, floods or large storms,” said lead author James Goff, visiting professor at the University of Southampton. “However, we know very little about whether prehistoric mass burial sites near coastlines could be the result of natural disasters or other causes such as war, famine and disease. This gave us our light bulb moment of developing an enhanced version of a modern forensic test to use on ancient bones.”
Collaborating with Pedro Andrade at the Universidad de Concepción in Chile, Goff scanned archaeological papers for records of mass burial sites near coastlines, settling on a site just south of Tocopilla on the Chilean coastline known to contain a grave with three well preserved skeletons.
The individual they studied was a male hunter-gather aged between 35 and 45. The condition of his bones suggested he was a fisherman as there were signs of frequent harpooning, rowing and harvesting of shellfish. This made him the ideal candidate to study for signs of drowning and for evidence of the event that led to his death.
In addition to the diatom test, Goff and colleagues also carried out wide-ranging microscopic analysis of bone marrow extracted from the man. This allowed them to search for a greater range of microscopic particles that could possibly provide more insight into the cause of his death.
As described in their paper, published in the Journal of Archaeological Science, the researchers indeed found a variety of marine particles in the marrow that suggested he drowned in saltwater, including fossilized algae, parasite eggs and sediment. The researchers say none of this evidence would have been detected by the standard diatom test.
Not only was the team able to determine that the fisherman drowned, they were able to determine how he drowned.
“By looking at what we found in his bone marrow, we know that he drowned in shallow saltwater,” explained Goff. “We could see that the poor man swallowed sediment in his final moments and sediment does not tend to float around in sufficient concentrations in deeper waters.”
This evidence, in addition to the fact that drowning was not the cause of death for the two others the fisherman was buried with, leads the team to believe he died in a marine accident rather than in a major catastrophic event.
Beyond this fisherman, the scientists said they believe this new technique can be used for ancient mass burial sites around the world to get a better picture of the lives of people in coastal communities throughout history.
“In taking more time over the forensic technique and testing for a broader range of beasties inside the prehistoric bones, we’ve cracked open a whole new way to do things,” said Goff. “This can help us understand much more about how tough it was living by the coast in pre-historic days, and how people there were affected by catastrophic events, just as we are today. There are many coastal mass burial sites around the world where excellent archaeological studies have been carried out but the fundamental question of what caused so many deaths has not been addressed. Now, we can take this new technique out around the world and potentially re-write prehistory.”
Photo: The Neolithic fisherman in burial site. Credit: Pedro Andrade