Human decomposition is a natural process beginning at death, involving a series of transforming changes. This article explores what happens in the days and weeks following death.
The Initial Stages of Change
Immediately after death, the body undergoes several alterations. Pallor mortis, a paleness of the skin, occurs within 15 to 120 minutes as blood stops circulating. The body’s temperature begins to drop, a process called algor mortis, cooling at 1.5°F (0.83°C) per hour until it matches the ambient environment. Livor mortis, or lividity, involves blood pooling in dependent areas due to gravity, leading to a purplish-red discoloration apparent within an hour and fixing in 6 to 8 hours.
Following these initial changes, rigor mortis sets in, causing muscles to stiffen. This occurs as adenosine triphosphate (ATP), the energy molecule for muscle relaxation, depletes after death. Rigor mortis usually begins 2 to 6 hours post-mortem, starting in smaller muscles and reaching full rigidity within 8 to 12 hours. This stiffness then gradually dissipates, resolving within 24 to 36 hours as muscle proteins break down.
The Body at Two Weeks
By two weeks, the body enters an advanced stage of decomposition, often called the “bloat” or “active decay” stage. Significant changes are apparent. The body undergoes considerable bloating from accumulated gases like methane and hydrogen sulfide, produced by internal bacterial activity. This gas buildup can cause the torso and limbs to swell noticeably, sometimes doubling the body’s size.
Skin discoloration is pronounced, with a greenish tint appearing over the abdomen, spreading and darkening to a green-black marbling pattern as blood vessels become visible. Skin slippage is also common, where outer skin layers detach from underlying tissues, resembling severe sunburn or blisters. This happens as enzymes and bacteria break down cellular connections. Fluids may also purge from body orifices due to internal pressure.
Internally, tissues and organs undergo liquefaction due to continued putrefaction. The brain can become soft and liquefied. Organs like the liver may develop a spongy or “swiss-cheese-like” appearance from gas formation. The intestines distend further with gas, and soft tissues continue to break down, leading to significant loss of body mass as fluids drain.
Factors Affecting Decomposition Rate
The rate of decomposition is highly variable, influenced by external environmental conditions and intrinsic body factors.
Temperature
Temperature is a primary accelerator of decomposition. Warmer temperatures promote faster bacterial growth and enzymatic reactions, speeding up tissue breakdown. Colder temperatures, especially freezing conditions, can significantly slow or halt the process.
Humidity
Humidity also plays a role. Humid environments facilitate rapid bacterial growth and insect activity, leading to faster decay. Dry conditions can lead to mummification, preserving tissues by desiccation.
Water Presence
The presence of water can alter decomposition. Submerged bodies often decompose slower than those in air due to cooler temperatures and reduced oxygen, though water can also accelerate skin slippage.
Burial Depth
Burial depth affects the rate. Shallow burial or exposure to air generally results in faster decomposition compared to deeper burial, which limits insect access and airflow.
Body Composition
Body size and composition also influence decomposition. Higher fat content can lead to slower decay due to insulation, or faster decay in certain conditions due to fat breakdown.
Clothing
Clothing can impact the process. It sometimes insulates the body, slowing heat loss, or can accelerate insect activity if it provides a protected environment.
Cause of Death
The cause of death can also be a factor. Deaths involving infection can accelerate decomposition due to existing bacterial activity.
The Role of Decomposers
Living organisms drive decomposition by breaking down tissues. Bacteria, both internal (especially from the gut) and external, are the primary internal decomposers. After death, the immune system ceases, allowing these bacteria to proliferate and digest tissues in a process known as putrefaction. As oxygen levels decrease, anaerobic bacteria become more prevalent, producing gases and foul-smelling compounds like putrescine and cadaverine.
Insects, especially flies, are significant external decomposers. Blowflies and flesh flies are among the first to arrive, attracted by decomposition odors within minutes to hours of death. They lay eggs in natural orifices and open wounds; these eggs hatch into larvae, or maggots, which consume decaying tissue, accelerating breakdown. As decomposition progresses, other insects like beetles, including carrion and dermestid beetles, arrive to feed on drier tissues, hair, and skin. These biological agents work with physical and chemical processes to recycle the body’s organic matter.