Decomposition

Decomposition

Overview
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome
Biome
Biomes are climatically and geographically defined as similar climatic conditions on the Earth, such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems. Some parts of the earth have more or less the same kind of abiotic and biotic factors spread over a...

. Bodies of living organisms begin to decompose shortly after death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. The science which studies decomposition is generally referred to as taphonomy
Taphonomy
Taphonomy is the study of decaying organisms over time and how they become fossilized . The term taphonomy was introduced to paleontology in 1940 by Russian scientist Ivan Efremov to describe the study of the transition of remains, parts, or products of organisms, from the biosphere, to the...

from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 word taphos, meaning tomb.

One can differentiate abiotic and biotic decomposition or biodegradation
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...

.
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Encyclopedia
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome
Biome
Biomes are climatically and geographically defined as similar climatic conditions on the Earth, such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems. Some parts of the earth have more or less the same kind of abiotic and biotic factors spread over a...

. Bodies of living organisms begin to decompose shortly after death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. The science which studies decomposition is generally referred to as taphonomy
Taphonomy
Taphonomy is the study of decaying organisms over time and how they become fossilized . The term taphonomy was introduced to paleontology in 1940 by Russian scientist Ivan Efremov to describe the study of the transition of remains, parts, or products of organisms, from the biosphere, to the...

from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 word taphos, meaning tomb.

One can differentiate abiotic and biotic decomposition or biodegradation
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...

. The former one means "degradation of a substance by chemical or physical processes, eg hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...

). The latter one means "the metabolic breakdown of materials into simpler components by living organisms", typically by microorganisms.

Stages


Five general stages are used to describe the process of decomposition: Fresh, Bloat, Active and Advanced Decay, and Dry/Remains. The general stages of decomposition are coupled with two stages of chemical decomposition: autolysis and putrefaction
Putrefaction
Putrefaction is one of seven stages in the decomposition of the body of a dead animal. It can be viewed, in broad terms, as the decomposition of proteins, in a process that results in the eventual breakdown of cohesion between tissues and the liquefaction of most organs.-Description:In terms of...

. These two stages contribute to the chemical process of decomposition
Chemical process of decomposition
Decomposition is a process that begins immediately after death and involves the destruction of soft tissue, leaving behind skeletonized remains. The chemical process of decomposition is complex and involves the breakdown of soft tissue, as the body passes through the sequential stages of...

, which breaks down the main components of the body

Fresh


The fresh stage begins immediately after the heart stops beating. Since blood is no longer being pumped through the body it drains to the dependent portions of the body, under gravity, creating an overall bluish-purple discolouration termed livor mortis
Livor mortis
Livor mortis , postmortem lividity , or hypostasis is one of the signs of death...

 or, more commonly, lividity. Shortly after death, within three to six hours, the muscular tissues become rigid and incapable of contraction which is known as rigor mortis
Rigor mortis
Rigor mortis is one of the recognizable signs of death that is caused by a chemical change in the muscles after death, causing the limbs of the corpse to become stiff and difficult to move or manipulate...

. From the moment of death, the body begins losing heat to the surrounding environment, resulting in an overall cooling called algor mortis
Algor mortis
Algor mortis is the reduction in body temperature following death. This is generally a steady decline until matching ambient temperature, although external factors can have a significant influence....

.

Once the heart stops, chemical changes occur within the body and result in changes in pH, causing cells to lose their structural integrity. The loss of cell structure brings about the release of cellular enzymes capable of initiating the breakdown of surrounding cells and tissues. This process is known as autolysis. Visible changes caused by decomposition are limited during the fresh stage, although autolysis may cause blisters to appear at the surface of the skin.

Oxygen present in the body is quickly depleted by the aerobic organisms found within. This creates an ideal environment for the proliferation of anaerobic organisms. Anaerobic organisms, originating in the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....

 and respiratory system
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...

, begin to transform carbohydrates, lipids, and proteins, to yield organic acids (propionic acid
Propionic acid
Propanoic acid is a naturally occurring carboxylic acid with chemical formula CH3CH2COOH. It is a clear liquid with a pungent odor...

, lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

) and gases (methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

, hydrogen sulphide, ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

). The process of microbial proliferation within a body is referred to as putrefaction
Putrefaction
Putrefaction is one of seven stages in the decomposition of the body of a dead animal. It can be viewed, in broad terms, as the decomposition of proteins, in a process that results in the eventual breakdown of cohesion between tissues and the liquefaction of most organs.-Description:In terms of...

 and leads to the second stage of decomposition, known as bloat.

Blowflies and flesh flies are the first carrion insects to arrive, and seek a suitable oviposition site.

Bloat


The bloat stage provides the first clear visual sign that microbial proliferation is underway. In this stage, anaerobic metabolism takes place, leading to the accumulation of gases, such as hydrogen sulphide, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, and methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

. The accumulation of gases within the bodily cavity causes the distention of the abdomen and gives a cadaver its overall bloated appearance. The gases produced also cause natural liquids and liquefying tissues to become frothy. As the pressure of the gases within the body increases, fluids are forced to escape from natural orifices, such as the nose, mouth, and anus, and enter the surrounding environment. The buildup of pressure may also cause rupturing of the skin.

Intestinal anaerobic bacteria transform haemoglobin into sulfhemoglobin and other colored pigments. The associated gases which accumulate within the body at this time aid in the transport of sulfhemoglobin throughout the body via the circulatory
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

 and lymphatic system
Lymphatic system
The lymphoid system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart. Lymphoid tissue is found in many organs, particularly the lymph nodes, and in the lymphoid follicles associated...

s, giving the body an overall marbled appearance.

If insects have access, maggots hatch and begin to feed on the body’s tissues. Maggot activity, typically confined to natural orifices and masses under the skin, causes the skin to slip and hair to detach from the skin. Maggot feeding, and the accumulation of gases within the body, eventually leads to post-mortem skin ruptures which will then further allow purging of gases and fluids into the surrounding environment. Ruptures in the skin allow oxygen to re-enter the body and provide more surface area for the development of fly larvae and the activity of aerobic microorganisms. The purging of gases and fluids results in the strong distinctive odours associated with decay.

Active Decay


Active decay is characterized by the period of greatest mass loss. This loss occurs as a result of both the voracious feeding of maggots and the purging of decomposition fluids into the surrounding environment. The purged fluids accumulate around the body and create a cadaver decomposition island (CDI). Liquefaction of tissues and disintegration become apparent during this time and strong odours persist. The end of active decay is signaled by the migration of maggots away from the body to pupate.

Advanced Decay


Decomposition is largely inhibited during advanced decay due to the loss of readily available cadaveric material. Insect activity is also reduced during this stage. When the carcass is located on soil, the area surrounding it will show evidence of vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...

 death. The CDI surrounding the carcass will display an increase in soil carbon and nutrients, such as phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

, potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

, calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

, and magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

; changes in pH; and a significant increase in soil nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

.

Dry/Remains


During the dry/remains stage, the resurgence of plant growth around the CDI may occur and is a sign that the nutrients present in the surrounding soil have not yet returned to their normal levels. All that remains of the cadaver at this stage is dry skin, cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

, and bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

s, which will become dry and bleached if exposed to the elements. If all soft tissue is removed from the cadaver, it is referred to as completely skeletonized
Skeletonization (forensics)
In forensics, skeletonization refers to the complete decomposition of the non-bony tissues of a corpse, leading to a bare skeleton. In a temperate climate, it usually requires three weeks to several years for a body to completely decompose into a skeleton, depending on factors such as temperature,...

, but if only portions of the bones are exposed, it is referred to as partially skeletonised.

Plant decomposition




Decomposition of plant matter occurs in many stages. It begins with leaching by water; the most easily lost and soluble carbon compounds are liberated in this process. Another early process is physical breakup or fragmentation of the plant material into smaller bits which have greater surface area for microbial colonization and attack. In smaller dead plants, this process is largely carried out by the soil invertebrate fauna, whereas in the larger plants, primarily parasitic life-forms such as insects and fungi play a major breakdown role and are not assisted by numerous detritivore
Detritivore
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...

 species.
Following this, the plant detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...

 (consisting of cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

, hemicellulose
Hemicellulose
A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...

, microbial products, and lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...

) undergoes chemical alteration by microbes. Different types of compounds decompose at different rates. This is dependent on their chemical structure
Chemical structure
A chemical structure includes molecular geometry, electronic structure and crystal structure of molecules. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together. Molecular geometry can range from the very simple, such as...

. For instance, lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...

 is a component of wood, which is relatively resistant to decomposition and can in fact only be decomposed by certain fungi, such as the black-rot fungi. Said fungi are thought to be seeking the nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 content of lignin rather than its carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 content. Lignin is one such remaining product of decomposing plants with a very complex chemical structure causing the rate of microbial breakdown to slow. Warmth determines the speed of plant decay, with the rate of decay increasing as heat increases, i.e. a plant in a warm environment will decay over a shorter period of time.
In most grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...

 ecosystems, natural damage from fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

, insects that feed on decaying matter, termites, grazing
Grazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...

 mammals, and the physical movement of animals through the grass are the primary agents of breakdown and nutrient cycling, while bacteria and fungi play the main roles in further decomposition.
The chemical aspects of plant decomposition always involve the release of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

.

Animal decomposition



Decomposition begins at the moment of death, caused by two factors: autolysis, the breaking down of tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

s by the body's own internal chemicals and enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s, and putrefaction
Putrefaction
Putrefaction is one of seven stages in the decomposition of the body of a dead animal. It can be viewed, in broad terms, as the decomposition of proteins, in a process that results in the eventual breakdown of cohesion between tissues and the liquefaction of most organs.-Description:In terms of...

, the breakdown of tissues by bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

. These processes release gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

es that are the chief source of the unmistakably putrid odor
Odor
An odor or odour is caused by one or more volatilized chemical compounds, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction. Odors are also commonly called scents, which can refer to both pleasant and unpleasant odors...

 of decaying animal tissue.

Most decomposers are bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 or fungi, though scavenger
Scavenger
Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...

s also play an important role in decomposition if the body is accessible to insects and other animals. The most important insects that are involved in the process include the flesh-flies
Flesh-fly
Flies of the Diptera family Sarcophagidae are commonly known as flesh flies. Most flesh flies breed in carrion, dung, or decaying material, but a few species lay their eggs in the open wounds of mammals; hence their common name...

 (Sarcophagidae) and blow-flies
Blow-fly
Calliphoridae are insects in the Order Diptera, family Calliphoridae...

 (Calliphoridae), such as the green-bottle fly seen in the summer. The most important non-insect animals that are typically involved in the process include larger scavengers, such as: coyote
Coyote
The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...

s, dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

s, wolves, fox
Fox
Fox is a common name for many species of omnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail .Members of about 37 species are referred to as foxes, of which only 12 species actually belong to...

es, rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

s, crows and vultures. Some of these scavengers also remove and scatter bones, which they ingest at a later time.

Food decomposition


The decomposition of food, called spoilage in this context, is an important field of study within food science
Food science
Food science is a study concerned with all technical aspects of foods, beginning with harvesting or slaughtering, and ending with its cooking and consumption, an ideology commonly referred to as "from field to fork"...

.

Importance to forensics


Various sciences study the decomposition of bodies under the general rubric of forensics
Forensics
Forensic science is the application of a broad spectrum of sciences to answer questions of interest to a legal system. This may be in relation to a crime or a civil action...

 because the usual motive for such studies is to determine the time and cause of death for legal
Law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

 purposes:
  • Forensic taphonomy specifically studies the processes of decomposition in order to apply the biological and chemical principles to forensic cases in order to determine post-mortem interval (PMI), post-burial interval as well as to locate clandestine graves.
  • Forensic pathology
    Forensic pathology
    Forensic pathology is a branch of pathology concerned with determining the cause of death by examination of a corpse. The autopsy is performed by the pathologist at the request of a coroner or medical examiner usually during the investigation of criminal law cases and civil law cases in some...

     studies the clues to the cause of death found in the corpse as a medical
    Medicine
    Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

     phenomenon.
  • Forensic entomology
    Forensic entomology
    Forensic entomology is the application and study of insect and other arthropod biology to criminal matters. It is primarily associated with death investigations; however, it may also be used to detect drugs and poisons, determine the location of an incident, and find the presence and time of the...

     studies the insects and other vermin
    Vermin
    Vermin is a term applied to various animal species regarded by some as pests or nuisances and especially to those associated with the carrying of disease. Since the term is defined in relation to human activities, which species are included will vary from area to area and even person to person...

     found in corpses; the sequence in which they appear, the kinds of insects, and where they are found in their life cycle are clues that can shed light on the time of death, the length of a corpse's exposure, and whether the corpse was moved.
  • Forensic anthropology
    Forensic anthropology
    Forensic anthropology is the application of the science of physical anthropology and human osteology in a legal setting, most often in criminal cases where the victim's remains are in the advanced stages of decomposition. A forensic anthropologist can assist in the identification of deceased...

     is the branch of physical anthropology
    Physical anthropology
    Biological anthropology is that branch of anthropology that studies the physical development of the human species. It plays an important part in paleoanthropology and in forensic anthropology...

     that studies skeletons and human remains, usually to seek clues as to the identity, race, and sex of their former owner.


The University of Tennessee Anthropological Research Facility (better known as the Body Farm) in Knoxville, Tennessee
Knoxville, Tennessee
Founded in 1786, Knoxville is the third-largest city in the U.S. state of Tennessee, U.S.A., behind Memphis and Nashville, and is the county seat of Knox County. It is the largest city in East Tennessee, and the second-largest city in the Appalachia region...

 has a number of bodies laid out in various situations in a fenced-in plot near the medical center. Scientists at the Body Farm
Body Farm
A body farm is a research facility where human decomposition can be studied in a variety of settings. The aim is to gain a better understanding of the decomposition process, permitting the development of techniques for extracting information from human remains...

 study how the human body decays in various circumstances to gain a better understanding into decomposition.

Exposure to the elements


A dead body that has been exposed to the open elements, such as water and air, will decompose more quickly and attract much more insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

 activity than a body that is buried or confined in special protective gear or artifacts. This is due, in part, to the limited number of insects that can penetrate a coffin and the lower temperatures under soil.

The rate and manner of decomposition in an animal body is strongly affected by a number of factors. In roughly descending degrees of importance, they are:
  • Temperature
    Temperature
    Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

    ;
  • The availability of oxygen
    Oxygen
    Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

    ;
  • Prior embalming
    Embalming
    Embalming, in most modern cultures, is the art and science of temporarily preserving human remains to forestall decomposition and to make them suitable for public display at a funeral. The three goals of embalming are thus sanitization, presentation and preservation of a corpse to achieve this...

    ;
  • Cause of death;
  • Burial
    Burial
    Burial is the act of placing a person or object into the ground. This is accomplished by excavating a pit or trench, placing an object in it, and covering it over.-History:...

    , depth of burial, and soil type;
  • Access by scavenger
    Scavenger
    Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...

    s;
  • Trauma
    Physical trauma
    Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...

    , including wound
    Wound
    A wound is a type of injury in which skin is torn, cut or punctured , or where blunt force trauma causes a contusion . In pathology, it specifically refers to a sharp injury which damages the dermis of the skin.-Open:...

    s and crushing blows;
  • Humidity
    Humidity
    Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...

    , or wetness;
  • Rain
    Rain
    Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...

    fall;
  • Body size and weight;
  • Clothing
    Clothing
    Clothing refers to any covering for the human body that is worn. The wearing of clothing is exclusively a human characteristic and is a feature of nearly all human societies...

    ;
  • The surface on which the body rests;
  • Foods/objects inside the specimen's digestive tract (bacon compared to lettuce).


The speed at which decomposition occurs varies greatly. Factors such as temperature, humidity, and the season of death all determine how fast a fresh body will skeletonize or mummify. A basic guide for the effect of environment on decomposition is given as Casper's Law (or Ratio): if all other factors are equal, then, when there is free access of air a body decomposes twice as fast than if immersed in water and eight times faster than if buried in earth. Ultimately, the rate of bacterial decomposition acting on the tissue will be depend upon the temperature of the surroundings. Colder temperatures decrease the rate of decomposition while warmer temperatures increase it.

The most important variable is a body's accessibility to insects, particularly flies. On the surface in tropical areas, invertebrates alone can easily reduce a fully fleshed corpse to clean bones in under two weeks. The skeleton itself is not permanent; acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

s in soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

s can reduce it to unrecognizable components. This is one reason given for the lack of human remains found in the wreckage of the Titanic, even in parts of the ship considered inaccessible to scavengers. Freshly skeletonized bone is often called "green" bone and has a characteristic greasy feel. Under certain conditions (normally cool, damp soil), bodies may undergo saponification
Saponification
Saponification is a process that produces soap, usually from fats and lye. In technical terms, saponification involves base hydrolysis of triglycerides, which are esters of fatty acids, to form the sodium salt of a carboxylate. In addition to soap, such traditional saponification processes...

 and develop a waxy substance called adipocere
Adipocere
Adipocere , also known as corpse, grave or mortuary wax, is a wax-like organic substance formed by the anaerobic bacterial hydrolysis of fat in tissue, such as body fat in corpses...

, caused by the action of soil chemicals on the body's protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s and fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

s. The formation of adipocere slows decomposition by inhibiting the bacteria that cause putrefaction.

In extremely dry or cold conditions, the normal process of decomposition is halted – by either lack of moisture or temperature controls on bacterial and enzymatic action – causing the body to be preserved as a mummy
Mummy
A mummy is a body, human or animal, whose skin and organs have been preserved by either intentional or incidental exposure to chemicals, extreme coldness , very low humidity, or lack of air when bodies are submerged in bogs, so that the recovered body will not decay further if kept in cool and dry...

. Frozen mummies commonly restart the decomposition process when thawed (see Ötzi the Iceman
Ötzi the Iceman
Ötzi the Iceman , Similaun Man, and Man from Hauslabjoch are modern names for a well-preserved natural mummy of a man who lived about 5,300 years ago. The mummy was found in September 1991 in the Ötztal Alps, near Hauslabjoch on the border between Austria and Italy. The nickname comes from the...

), whilst heat-desiccated mummies remain so unless exposed to moisture.

The bodies of newborns who never ingested food are an important exception to the normal process of decomposition. They lack the internal microbial flora that produce much of decomposition and quite commonly mummify if kept in even moderately dry conditions.

Artificial preservation


Embalming
Embalming
Embalming, in most modern cultures, is the art and science of temporarily preserving human remains to forestall decomposition and to make them suitable for public display at a funeral. The three goals of embalming are thus sanitization, presentation and preservation of a corpse to achieve this...

 is the practice of delaying decomposition of human and animal remains. Embalming slows decomposition somewhat, but does not forestall it indefinitely. Embalmers typically pay great attention to parts of the body seen by mourners, such as the face and hands. The chemicals used in embalming repel most insects, and slow down bacterial putrefaction by either killing existing bacteria in or on the body themselves or by "fixing" cellular proteins, which means that they cannot act as a nutrient source for subsequent bacterial infections. In sufficiently dry environments, an embalmed body may end up mummified
Mummy
A mummy is a body, human or animal, whose skin and organs have been preserved by either intentional or incidental exposure to chemicals, extreme coldness , very low humidity, or lack of air when bodies are submerged in bogs, so that the recovered body will not decay further if kept in cool and dry...

 and it is not uncommon for bodies to remain preserved to a viewable extent after decades. Notable viewable embalmed bodies include those of:
  • Eva Peron
    Eva Perón
    María Eva Duarte de Perón was the second wife of President Juan Perón and served as the First Lady of Argentina from 1946 until her death in 1952. She is often referred to as simply Eva Perón, or by the affectionate Spanish language diminutive Evita.She was born in the village of Los Toldos in...

     whose body was injected with paraffin
    Paraffin
    In chemistry, paraffin is a term that can be used synonymously with "alkane", indicating hydrocarbons with the general formula CnH2n+2. Paraffin wax refers to a mixture of alkanes that falls within the 20 ≤ n ≤ 40 range; they are found in the solid state at room temperature and begin to enter the...

     and was kept perfectly preserved for many years, and still is as far as is known (her body is no longer on public display).
  • Lenin, whose body was kept submerged in a special tank of fluid for decades and is on public display in Lenin's Mausoleum
    Lenin's Mausoleum
    Lenin's Mausoleum also known as Lenin's Tomb, situated in Red Square in the center of Moscow, is the mausoleum that serves as the current resting place of Vladimir Lenin. His embalmed body has been on public display there since shortly after his death in 1924...

    .
  • Other communist leaders such as Mao Zedong
    Mao Zedong
    Mao Zedong, also transliterated as Mao Tse-tung , and commonly referred to as Chairman Mao , was a Chinese Communist revolutionary, guerrilla warfare strategist, Marxist political philosopher, and leader of the Chinese Revolution...

    , Kim Il-sung
    Kim Il-sung
    Kim Il-sung was a Korean communist politician who led the Democratic People's Republic of Korea from its founding in 1948 until his death in 1994. He held the posts of Prime Minister from 1948 to 1972 and President from 1972 to his death...

     and Ho Chi Minh
    Ho Chi Minh
    Hồ Chí Minh , born Nguyễn Sinh Cung and also known as Nguyễn Ái Quốc, was a Vietnamese Marxist-Leninist revolutionary leader who was prime minister and president of the Democratic Republic of Vietnam...

     have also had their cadavers preserved in the fashion of Lenin's preservation and are now displayed in their respective mausoleums.
  • Pope John XXIII
    Pope John XXIII
    -Papal election:Following the death of Pope Pius XII in 1958, Roncalli was elected Pope, to his great surprise. He had even arrived in the Vatican with a return train ticket to Venice. Many had considered Giovanni Battista Montini, Archbishop of Milan, a possible candidate, but, although archbishop...

    , whose preserved body can be viewed in St. Peter's Basilica
    St. Peter's Basilica
    The Papal Basilica of Saint Peter , officially known in Italian as ' and commonly known as Saint Peter's Basilica, is a Late Renaissance church located within the Vatican City. Saint Peter's Basilica has the largest interior of any Christian church in the world...

    .
  • Padre Pio, whose body was injected with formalin prior to burial in a dry vault from which he was later removed and placed on public display at the San Giovanni Rotondo
    San Giovanni Rotondo
    San Giovanni Rotondo is the name of a city and comune in the province of Foggia, Puglia region, southern Italy. As of 2006 it had a population of 26,442....

    .

Environmental preservation


A body buried in a sufficiently dry environment may be well preserved for decades. This was observed in the case for murdered civil rights
Civil rights
Civil and political rights are a class of rights that protect individuals' freedom from unwarranted infringement by governments and private organizations, and ensure one's ability to participate in the civil and political life of the state without discrimination or repression.Civil rights include...

 activist Medgar Evers
Medgar Evers
Medgar Wiley Evers was an African American civil rights activist from Mississippi involved in efforts to overturn segregation at the University of Mississippi...

, who was found to be almost perfectly preserved over 30 years after his death, permitting an accurate autopsy
Autopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...

 when the case of his murder was re-opened in the 1990s.

Bodies submerged in a peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...

 bog
Bog
A bog, quagmire or mire is a wetland that accumulates acidic peat, a deposit of dead plant material—often mosses or, in Arctic climates, lichens....

 may become naturally "embalmed", arresting decomposition and resulting in a preserved specimen known as a bog body
Bog body
Bog bodies, which are also known as bog people, are the naturally preserved human corpses found in the sphagnum bogs in Northern Europe. Unlike most ancient human remains, bog bodies have retained their skin and internal organs due to the unusual conditions of the surrounding area...

. The time for an embalmed body to be reduced to a skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

 varies greatly. Even when a body is decomposed, embalming treatment can still be achieved (the arterial system decays more slowly) but would not restore a natural appearance without extensive reconstruction and cosmetic work, and is largely used to control the foul odors due to decomposition.

In some cases, bodies are inexplicably preserved (with no technique used) for decades or centuries and appear almost the same as when they died. This is known as incorruptibility
Incorruptibility
Incorruptibility is a Roman Catholic and Eastern Orthodox belief that supernatural intervention allows some human bodies to avoid the normal process of decomposition after death as a sign of their holiness...

. It is not known, though, how long a body can stay free of decay.

See also

  • Cadaverine
    Cadaverine
    Cadaverine is a foul-smelling compound produced by protein hydrolysis during putrefaction of animal tissue. Cadaverine is a toxic diamine with the formula NH25NH2, which is similar to putrescine...

  • Decompiculture
    Decompiculture
    The term decompiculture is a neologism coined by forestry professor Timothy Myles of the Urban Entomology Program at the University of Toronto and refers to how decomposing organisms, like termites, could be grown or cultured for a variety of uses....

  • Embalming
    Embalming
    Embalming, in most modern cultures, is the art and science of temporarily preserving human remains to forestall decomposition and to make them suitable for public display at a funeral. The three goals of embalming are thus sanitization, presentation and preservation of a corpse to achieve this...

  • Putrescine
    Putrescine
    Putrescine is a foul-smelling organic chemical compound NH24NH2 that is related to cadaverine; both are produced by the breakdown of amino acids in living and dead organisms and both are toxic in large doses...

  • Staling
    Staling
    Staling, or "going stale", is a chemical and physical process in bread and other foods that reduces their palatability. Stale bread is dry and leathery.-Mechanism and effects:...

  • Microbiology of decomposition
    Microbiology of decomposition
    Microbiology of decomposition is the study of all microorganisms involved in the chemical and physical processes during which organic matter is broken down and reduced to its original elements....


External links