Scientists are figuring out what makes human corpses smell like 'death'

When natural disasters strike, first aid workers are tasked with an especially morbid mission: to find and remove dead bodies.

They have to sift through the rubble of toppled buildings and charred forests to locate, ID, and dispose of human remains.

It’s a hard job, so they enlist the help of scent-sniffing dogs to detect the bodies.

But training dogs to pick up the scent of cadavers is extremely challenging because we still don’t fully understand what chemicals make up the human “smell of death.”

Scientists from the University of Leuven in Belgium have gotten one step closer, however, after analysing dozens of rotting human and animal body parts. From this analysis, they isolated 452 chemical compounds associated with death, and of those, five appear to be specific to humans. They published their results on September 16 in the journal PLOS ONE.

To compare the smells of different corpses, the team collected a variety of human and animal body parts — tissues and organs from humans and pigs, as well as the remains of dead mice, rabbits, moles, frogs, birds, and even a sturgeon and a turtle. The human body parts came from autopsies performed at a hospital in Belgium. Then they sealed the specimens in glass jars and put them in a closet.

The team then analysed the gases emanating from the rotting body parts on a regular schedule for six months. After comparing the hundreds of odorous compounds they found wafting from the samples, they identified eight compounds specific to humans and pigs. They then sorted these further and identified five compounds associated with the degradation of muscle, fats, and carbohydrates that were present in the human remains but not in the pig’s.

Researchers have been trying for decades to figure out what makes that human death smell so … human. But finding the answer to this question has been challenging.

When bodies decompose, they release distinct chemical cocktails that waft into the nose. Many factors — such as the collection of bacteria in and on the body, air temperature and humidity, the type of soil that’s touching the body, and whether or not it is submerged — affect the makeup of the compounds hovering around the corpse.

Human bodies are also hard to come by in research labs, so scientists mainly analyse the death scent of dead pigs, which have similar skin, hair, gut bacteria, and muscle-to-body fat ratios as humans. Because these researchers compared actual decomposing human tissue with those of other animals, they were able to use the process of elimination to figure out which compounds are only present in humans.

These new results — which could provide new training materials for dogs or even help develop a machine that could electronically sniff out a corpse — have some limitations. The size of the jars meant that the team could only analyse parts of organs and tissues, rather than entire corpses, which could have limited the chemical compounds that were released.

They also performed the study in a controlled lab environment, rather than in nature, which could have evoked a different chemical response.

Nevertheless, it’s an exciting addition to the research aiming to uncover the human death smell — which unfortunately has proven rotten for years.

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