Buzz
From decaying corpses infested with maggots to putrid bodies releasing unbearable odors, the decomposition of the human body often feels like something straight out of a horror film, a crime series, or a nightmare. Our simultaneous intrigue and disgust with this process has sparked numerous myths and urban legends. (For the record, hair and nails don't continue growing after death, and no, bodies don’t sit up on mortuary tables.) Here are nine captivating facts that help explain the journey from flesh to bone to dust.
1. DECOMPOSITION BEGINS ALMOST IMMEDIATELY AFTER DEATH.
Within about four minutes of a person passing away, the lack of oxygen sets off a chain of events at the cellular level: Carbon dioxide and acidity levels rise in the bloodstream, and harmful wastes accumulate, poisoning the cells. Enzymes inside the cells then start to break them down. Organs rich in enzymes and water, like the liver and brain, become the first to undergo this process.
One of the earliest visible signs of death is the clouding of the eyes, caused by the cessation of fluids and oxygen reaching the corneas. This can occur within 10 minutes [PDF] of death.
2. DECOMPOSITION OCCURS IN FIVE DISTINCT PHASES.
The initial phase is known as fresh. During this stage, autolysis, or "self-digestion," takes place: The cells rupture due to enzymatic activity, causing fluids to leak out. Fluid-filled blisters form on the skin, which can peel off in large sheets.
At the same time, anaerobic bacteria from the gut start breaking down the cells, leading into the second phase of decomposition: bloat. As these bacteria continue their work, gases build up in the intestines, causing surrounding tissues to swell. The gases react with hemoglobin, the protein in red blood cells, creating a green pigment in the veins ("marbling"), and the skin turns green, then black.
In the third phase, active decomposition, tissues begin to liquefy, and decomposition fluids begin to leak out through body openings. As Dawnie Wolfe Steadman, director of the Forensic Anthropology Center at the University of Tennessee, Knoxville, explains, the primary cause of tissue loss is the activity of fly maggots, which feed on the tissues, and bacteria.
Advanced decomposition occurs when most of the soft tissues have decomposed, the remaining skin becomes dry and leathery, and the skeleton becomes visible, thanks to the continued efforts of insects. "Although the fly maggots no longer have much to consume, other insects like beetles arrive," says Steadman. "They are capable of breaking down the more resilient soft tissues, such as tendons, ligaments, and even cartilage."
Skeletal decay marks the final stage of the decomposition process. Various factors contribute to the breakdown or fragmentation of bones. For example, acidic soil dissolves a mineral compound called hydroxylapatite—a mix of calcium and phosphate—that makes up 70 percent of our bone material [PDF]. Additionally, bones can break down when subjected to physical forces like scavengers gnawing on them or the slow erosion from flowing water.
The duration of each stage above varies depending on factors like temperature, burial conditions, and the presence of microbes, insects, and scavengers. Active decomposition, in particular, is heavily influenced by temperature; flies lay eggs in warmer months, so decomposition tends to slow down in colder climates. Bones usually start to bleach within the first year, and algae and moss may begin to grow on their surface. Large cracks often develop after about ten years.
3. RIGOR MORTIS IS A TEMPORARY PHENOMENON.
Viewers of shows like Law & Order: SVU are probably familiar with rigor mortis, the stiffening of the body’s muscles after death. It begins within two to six hours, starting in the face and neck, and gradually spreads to the limbs. Rigor mortis occurs because two types of fibers in our muscle cells—actin and myosin—become tightly bound by chemical bonds that form as the pH levels in the cells decrease, causing inflexibility [PDF]. However, this rigidity fades within 1 to days, as the bonds between the muscle fibers break and the muscles relax, beginning with the face. During this process, the body may release feces and urine.
Rigor mortis sets in more rapidly and lasts longer in cooler temperatures than in warmer ones; one study found that rigor persisted for 10 days in bodies stored at 39°F in a mortuary. The circumstances leading up to death can also affect rigor: A high fever will shorten its duration, while intense physical activity will cause it to start sooner. These effects are likely the result of decreased levels of ATP (adenosine triphosphate), a cellular energy source, and increased lactic acid levels, which lower the pH in muscle cells.
4. DECOMPOSITION DOESN'T SMELL AS TERRIBLE AS YOU MIGHT THINK.
“People assume that bodies always reek,” says Melissa Connor, director of the Forensic Investigation Research Station at Colorado Mesa University. “But while there are certain times and stages when the remains are odorous, most of the time, the smell isn’t overwhelming.”
Foul-smelling gases accumulate during the bloat phase, but the odor fades as decomposition continues. According to Connor, in warmer weather, a corpse can pass through the more pungent stages in as little as 10 days.
A combination of gases creates the “sickly sweet” odor of death. Among these, putrescine and cadaverine—produced when bacteria break down the amino acids ornithine and lysine—emit particularly offensive smells. These gases can be absorbed through the skin and displace oxygen, posing a potential health risk for those working with decomposing bodies in confined spaces, such as under houses or in wells. A recent study suggests that putrescine may signal that death is imminent, triggering a “fight-or-flight” response.
5. DECOMPOSITION CAN SOMETIMES RESULT IN "SOAPY" CORPSES.
Another odorous by-product of decomposition is a waxy substance known as adipocere. Formed from fat under moist conditions through a process called saponification (the same chemical reaction used to create soap from fats), fresh adipocere has an ammonia-like smell, but as it dries, the odor dissipates. Philadelphia’s Mütter Museum holds a specimen of a corpse encased in adipocere, known as the Soap Lady, exhumed in 1875 from a city cemetery. The Smithsonian also possesses a male counterpart: Soapman, found in Philadelphia in 1875 during the construction of a train depot. He passed away around 1800.
6. THE 'NECROBIOME' COULD HELP US ESTIMATE TIME OF DEATH MORE PRECISELY.
Forensic entomologists rely on insects to determine time of death, but other biological indicators are also being studied. Steadman explains that forensic scientists are exploring how different bacterial species can influence decomposition, and whether bacteria can help identify individuals.
"Some researchers are investigating the necrobiome—the collection of bacteria and fungi that colonize a corpse—and determining if changes in the necrobiome can indicate the time of death," says Connor. By understanding which bacterial strains and other microbes are present during each phase of decomposition, scientists are developing a microbial clock to estimate the time since death. Some of these microbes originate from our own microbiome; others come from the surrounding soil, or are transferred to the body by flies, insects, and scavengers.
7. WITHOUT INSECTS OR BACTERIA, DECOMPOSITION CAN GRIND TO A HALT…
In December 1977, the Williamson County Sheriff was summoned to a historic estate called Two Rivers in Franklin, Tennessee, after the owners reported an unusual disturbance in the small graveyard there. Upon investigation, the sheriff’s department discovered a headless male corpse in formal attire resting atop a broken coffin belonging to a Confederate lieutenant colonel named William Shy, who had passed away in 1864. Forensic anthropologist William Bass was called in to examine the body.
In his book Death’s Acre, Bass describes the body as being in the early stages of decomposition, with the flesh still pink. He estimated the individual had been dead no longer than a year. However, there were peculiar details that intrigued Bass. The clothing was outdated, and the shoes were made from materials that weren’t common in modern times. The head was eventually found inside the coffin, and the teeth showed signs of pre-modern dental care. All of these clues led Bass to suspect the body belonged to Shy.
As it turned out, Bass was correct. Shy’s body had been exhumed by grave robbers. The 113-year-old corpse remained exceptionally well-preserved due to two factors: it had been embalmed, which slows decomposition (the degree of preservation depending on the embalming process), and the cast-iron coffin was sealed tightly, preventing the intrusion of insects and microbes that would have accelerated decomposition beyond the early stages.
In a similar case in May 2016, a sealed metal casket was unearthed from a backyard in San Francisco, where a home had been constructed on top of an old cemetery. Inside was the remarkably preserved body of a toddler named Edith Cook, who had died in 1876. While news reports don’t confirm whether Edith was embalmed, old advertisements from the casket’s manufacturer proudly claimed it provided “perfect protection from water and vermin.”
However, cast-iron coffins aren't immune to decomposition: In some instances, they've even exploded due to the buildup of gases during the bloat phase. This gas accumulation has also been a challenge for certain modern "protective" or "sealer" caskets.
8. … AND ENVIRONMENTAL FACTORS CAN AFFECT THE DECOMPOSITION PROCESS.
Certain environmental factors can be perfect for preserving bodies and even creating natural mummies—these are unique because their skin remains intact even through the active decomposition stage.
In European peat bogs, a combination of low oxygen, acidic water, and cool temperatures transforms corpses into bog bodies. While the acidic water breaks down bones, the tannins in the peat and the lack of oxygen preserve the skin in remarkable detail, capturing every wrinkle, expression, and fingerprint. Well-known examples include the Tollund Man and Lindow Man.
La Doncella, or 'The Maiden,' was an Inca teenager sacrificed in a ritual in the Andes Mountains in Argentina. Discovered in 1999, she was found head down, appearing to be peacefully asleep. Although she died over 500 years ago, her skin, hair, and clothing are nearly perfectly preserved. The high altitude, cold temperatures, and low oxygen levels contributed to the preservation of La Doncella's body.
Another testament to the preservative effects of the mountains is Ötzi, a natural mummy of a man who passed away about 5300 years ago. Found in 1991 in the Ötztal Valley Alps, he has been preserved almost completely. While the glacier ice dehydrated his body, his skin, organs, tissues, and bones remain remarkably well-preserved.
9. DISEASES THAT KILL THEIR HOSTS CAN ENDURE BEYOND DEATH.
Several viruses that cause diseases can survive even after their host has died. The Ebola virus, for example, remains highly contagious post-mortem, lingering in blood and bodily fluids. Any contact with broken skin or mucous membranes (such as those in the mouth or nose) of a healthy person is enough to transmit the virus. This is why the World Health Organization recommends that bodies of those infected with Ebola be buried swiftly and safely, with all involved in handling the body wearing protective equipment and ensuring the body is buried in a sealed coffin. Research has shown that the virus can last up to a week in deceased primates.
Norovirus, commonly known as the stomach flu, spreads similarly to Ebola, and it’s possible to contract influenza from the infected mucus of a deceased person. The smallpox virus can persist in the scabs of a dead person for up to a century, though it cannot be transmitted from the deceased to the living.
