Cemeteries: science six feet under

The biological and chemical mechanisms of post-mortem decomposition

"Three main phenomena will be visible in the short term, appearing within the first few hours. You will see the onset of rigour mortis: the body will stiffen in the position it was in at the time of death. If the person was sitting on a chair and you remove the chair, they will remain with their legs bent, as if they were still sitting [...] Then there are the colour changes [lividity]. In fact, the blood will flow downwards due to gravity. Consequently, in the lower areas, we will see a slightly purplish discolouration caused by the accumulation of blood, whilst in the higher areas and those under pressure, there will be no blood. For these two phenomena, we’re talking about a timeframe of roughly 24–48 hours. After that, they disappear. As for the third phenomenon, which is very important and is most commonly used to estimate the time of death, it is body temperature. From the moment of death, the body’s temperature is no longer maintained, so it will begin to fall, at least in an environment colder than 37°C. This gradual decrease takes place over roughly 48 hours, give or take, and so by measuring the body’s temperature, we can determine how long the person has been dead” – Damien Charabidzé

At the same time, the first living organisms to contribute to the decomposition of the body are not the scavenging insects found in the immediate environment, but our own gut bacteria, which begin to emerge from the intestines and spread everywhere.

“We’ll call this the phenomenon of autolysis. All the large molecules (proteins, lipids, carbohydrates) will be broken down into smaller ones, initially by our body’s own enzymes but also by enzymes produced by our bacteria. Subsequently, bacteria from the external environment may eventually arrive to continue the breakdown of these bodily molecules” – Ludovic Lesden

Link to the podcast (52 mins, in french)