Finding The Smell Of Death

By Debra Kelly on Saturday, October 31, 2015
Cemetery
“One day in the afternoon of the world, glum death will come and sit in you, and when you get up to walk, you will be as glum as death, but if you’re lucky, this will only make the fun better and the love greater.” —William Saroyan, “One Day in the Afternoon of the World”

In A Nutshell

The smell of death is a complicated, emotional thing, and science is working on a way to reproduce it. In addition to using the chemical combination that makes the smell of human death to create a synthetic substance to train cadaver dogs, researchers are also investigating some other fascinating phenomenon, like why the smell of hermit crab death makes its living neighbors salivate rather than run. It’s also being used to train soldiers by creating a more realistic simulation of the horrors they’ll face in active combat.

The Whole Bushel

Whether it’s the smell of the air after a spring rain, a crackling bonfire, or a newly opened rose, there are some smells that can trigger powerful memories. Other smells are important for other reasons.

In 2004, researchers kicked off the quest to isolate the smell of death. Led by a team in Greece and another on Tennessee’s Body Farm (a division of the University of Tennessee that studies the decomposition of the human body in various states, all in the name of forensic science), scientists have been trying to find out just what it is that creates the absolutely singular smell of human death.

In part, there’s a very practical reason for doing so. Discover just what it is that combines to make the smell of human death, and we’d be that much closer to being able to develop a synthetic version of the smell. That, in turn, would be of the utmost importance when it comes to training cadaver dogs. Currently, they’re usually trained using the smell of pig death, because they’re the animals that are closest to us in terms of crucial things like gut microbes, hair, and fat content.

It’s trickier than you might think, too. With help from the Belgian Disaster Victim Identification Team, 452 different organic compounds were isolated from the gases coming from decomposing bodies both human and animal. The process of elimination eventually led them to eight compounds (with names like diethyl disulfide and 3-methylthio-1-propanol) that were present only in pigs and humans. When the composition of pig gases were compared to humans, there were only five esters (like 3-methylbutyl pentanoate) that separated the two scents.

Isolating the bits needed to train cadaver dogs is only a small part of the fascinating if not gruesome science behind the smell of death.

For many animals, the smell of the death of their own species is a sign that there’s something very wrong. It’s associated with the presence of a predator, except in the hermit crab. A rather dark experiment by Michigan State University zoologist Mark Tran found that, contrary to what seemed like common sense, hermit crabs are universally excited by the smell of the death of their own species. Tran reported that he was pretty sure there was some sort of evolutionary process that had occurred in the development of the largely cannibalistic hermit crabs that made them view the smell of their own dead as a sign that a meal was quickly becoming available, instead of a sign that danger was around.

For humans, though, the smell of death is a powerfully emotional one—so powerful that the military is even including smell acclimation in some of its training methods. Most recently, it’s been partnering with the Institute for Creative Technologies and Hollywood to create a sort of smell-enhanced simulator, developed with some input from people who have seen active combat. One of the biggest criticisms of earlier prototypes was that there was no way simulated combat situations could feel like real combat without the smell of death.

The smell of death on the battlefield has been well-documented, with one of the most moving accounts coming from a 23-year-old nurse working at the Battle of Gettysburg in 1863.

Cornelia Hancock wrote, “A sickening, overpowering, awful stench announced the presence of the unburied dead upon which the July sun was mercilessly shining and at every step the air grew heavier and fouler until it seemed to possess a palpable horrible density that could be seen and felt and cut with a knife.”

She wrote that it was almost as though it were a malignant force with a mind of its own, killing those that were wounded in battle, those who waited for help to reach them.

Show Me The Proof

PLOS One: The Search for a Volatile Human Specific Marker in the Decomposition Process
American Association for the Advancement of Science: Researchers isolate the ‘human smell of death’
Smithsonian: Cannibalistic Hermit Crabs Salivate at the Smell of Their Dead
Popular Science: The Smell of War