Decomposition is not just about worms

Contrary to popular belief, bodies buried in coffins or vaults do not end up "eaten by worms." The decomposition of bodies is influenced by various factors, including temperature, presence or absence of oxygen, insects, and animals.

Chemical changes during decomposition

When a body decomposes, many chemical compounds are formed, some of which, such as adipocire, change the fate of the body. Burying bodies also has environmental consequences, as evidenced by the alteration of cemetery soils, which could also slow down the decomposition of bodies.

Human burial practices

In France, about 2000 deaths occur daily. Under natural conditions, the decomposition of animal bodies is mainly due to the action of scavengers and necrophagous insects. However, in most cases, human bodies undergo funeral procedures that isolate them from natural decomposition cycles.

Body composition and early decomposition

The body of an adult weighing 70 kg contains approximately 43 kg of water, 11 kg of proteins, 10 kg of fat, and 4 kg of minerals, which are mainly present in the bones. After death, these different elements undergo unavoidable and irreversible decomposition processes.

Visible signs of early putrefaction

The first visible signs of putrefaction are the change in skin color, which takes on a greenish hue in a few days, and the swelling of the abdomen. These are due to the proliferation of bacteria from the digestive tract, which spread and produce decomposition gases.

Insect activity and decomposition

For bodies exposed to the open air, the activity of insects becomes quickly visible, with the presence of flies and masses of maggots. Their development depends on the temperature: in summer, a few days may be enough to transform the body into a writhing mass.

Advanced stages of decomposition

The next stage is advanced putrefaction, which corresponds to the liquefaction of the organs. During the drying phase, the body gradually loses its water and flesh. Finally, the dry tissues and the organic matter of the bones end up decomposing. This is skeletonization.

Burial and decomposition conditions

Burial radically changes the decomposition processes. The placement in a coffin and then the burial isolate, at least initially, the corpse from its environment. In France, a minimum of 1 m of earth is required between the coffin lid and the surface of the ground.

Microbial activity in burial

The so-called Casper rule well summarizes this slow underground decomposition. Researchers followed the decomposition of 16 human bodies for a year, observing that microbial populations evolve throughout the decomposition. Oxygen availability is indeed a fundamental parameter of decomposition processes.

Adipocire formation

Under certain burial conditions with low levels of oxygen and high humidity, fatty tissues can also undergo a very specific transformation: the formation of adipocire. This pasty, gray substance is the result of chemical reactions naturally associated with putrefaction.

Decomposition of bones and teeth

Finally, bones and teeth decompose on much longer timescales, easily extending over centuries, explaining the contribution of these elements on the archaeological level. Their degradation relies on physical fragmentation: the bones "break" due to the progressive loss of their organic fraction.

Decomposition byproducts

The residues from decomposition are partly in liquid form: they are the cadaveric fluids and the leachates. To these decomposition liquids are added gaseous emissions. During cadaveric decomposition, the degradation of the different components of the body produces more than fifty volatile compounds.

Environmental impact of decomposition

Most decomposing microorganisms use the nitrogen present in the proteins of the bodies as a source of energy. This nitrogen is then released as ammonia. Under favorable conditions, the transformation of ammonia gives nitrates, then nitrates. These reactions are inhibited in deep burials where oxygen is rare.

Chemical contamination from burials

The ammonia and other decomposition residues accumulate in the soil and can contaminate groundwater. To these organic compounds from decomposition are added inputs such as those used for the making of coffins (glues and varnishes, fasteners, padding, etc.) and the preservation of bodies (formaldehyde).

Soil alteration and decomposition

We thus observe the presence of lead once used to waterproof coffins or arsenic, intended to preserve bodies and massively used in the 19th century. This alteration of the soil could be responsible for a slowing down of the decomposition of bodies.

Sensory experience for forensic pathologists

As a forensic pathologist, encountering death is part of our daily practice. The encounter with putrefied bodies also falls within this ordinary reality. However, it always has a particular dimension, in that, depending on the degree of degradation achieved, the body no longer presents the characteristics of a living being.

Variability in decomposition

The entire set of these perceptions is highly variable according to the state of degradation of the body, but also according to the conditions in which it has been preserved. Thus, for the same duration of preservation of a body in the ground, the results can differ significantly depending on whether embalming funeral care has been practiced.