The 17th century saw the beginning of several mysterious deaths, characterised by charred bodies and no signs of a fire having taken place. This sparked a fascination with the idea of ‘spontaneous human combustion’, and the term was coined in 1745 by Paul Rolli. Folklore ideas as to how one could burst into flames became prevalent. The excitement surrounding spontaneous human combustion (SHC) made its way into literature, one of the most famous examples being the death of Krook in Charles Dickens’ novel, Bleak House.
Over time, many scientists have tried to understand what causes SHC. This has been difficult, as the ‘combustion’ process has never been witnessed, and most of the information on this subject comes from historical accounts. Through analysis of these accounts, and post-mortem SHC victims, scientists devised theories as to how these seemingly unprompted burns appeared on these bodies.
Characterising SHC
Bodies that underwent SHC share similar characteristics. The middle area of the body, including the clothes in that area, becomes burned. This is because it tends to be the area of the body with the most fat, which is why the extremities of the body often remain unaffected. Upon closer examination of the tissue, there are no signs of an inflammatory reaction that could have led to the burns. This analysis also showed that SHC is not a cause of death; it is a postmortem event. This is indicated by a lack of soot in the airways or carbon monoxide saturating the haemoglobin in the blood.
Furthermore, the immediate surroundings of the body show no trace of a fire. However, a heat source, such as a fireplace, a cigarette, or a stove, can be found near the body, removing any spontaneity associated with the burning. Often, alcohol was found to saturate the postmortem tissues, but the involvement of alcohol in this process was negated, given that SHC without alcohol in the tissues has also occurred. However, in some cases, severe intoxication could be the reason why sources of open flame are found close to the body.
Taken together, these signs have been used to try to find a scientific explanation for SHC.
Folklore ideas about SHC
Before scientists questioned SHC, many believed it was a divine sign from God. The victims of this so-called divine intervention were often elderly, lazy women who drank a lot of alcohol. It was believed that burning of the body, but preservation of the surroundings, was a moral lesson to these women to not indulge in vices such as alcohol and instead become socially acceptable. This theory became so widespread that scientists embraced it. In fact, a French doctor who worked with spontaneously combusted bodies, Le Cât, suggested the idea of divine punishment for overindulgence.
It was thought specifically to be phosphorus in the alcohol that ignited the fire in the body. However, at this time, the toxicity of phosphorus was unknown. The implausibility of this theory allowed the later application of actual science to SHC.
The wick effect theory
The most plausible causes found for SHC involved the burning of fat. Of the three combustible parts of the body (soft tissue, bone and fat), fat is the most combustible constituent. An earlier theory involving this concept was conceived by a French surgeon, Dupuytren. He claimed that people’s clothing caught fire, causing the underlying fat to melt and fuel the body’s combustion.
These ideas surrounding fat and clothing led to the conception of the wick effect theory. This theory states that an external heat source causes the subject’s clothing to burn, which subsequently causes the skin to split and the fat underneath to melt. Much like a candle wick soaking up melted wax to keep a candle burning, the clothing soaks up fat to sustain the slow burning of the body. Body fat burns at around 250̊ C. But during the wick effect, the fat is not set alight, it is liquified. So, to sustain the ignition of the subject’s clothing, the fat’s temperature can be as low as 24̊ C.
To validate the significance of the wick effect, a model was created. Layers of human fat, skin and clothing were wrapped around a test tube. When set alight, the fat slowly combusts without a visible flame. Another experiment involved the burning of a pig carcass wrapped in a blanket. The fat and bones were burned in a slow, sustained fire, but the surroundings remained undamaged. From this evidence, the wick effect became the accepted mechanism behind SHC.
Alternative SHC hypotheses
Despite the consensus around the wick effect causing SHC, alternative hypotheses emerged as to what may cause bodies to spontaneously combust. One theory claimed that the bursting of mitochondria caused the release of hydrogen and oxygen in the body, thus creating the fuel for a fire. This was said to be triggered by a trance, and so was dismissed for having no scientific basis.
Another strange SHC theory claimed that a non-existent particle called a ‘pyrotron’ acted on cells, causing a chain reaction that led to the burning of the body.
An accumulation of acetone in the blood (known as ketosis) was another theorised cause of SHC. This was quickly dispelled, given that SHC victims tended not to be prone to hypoglycaemia, a condition where someone has a deficiency of glucose in their bloodstream, and therefore would not undergo ketosis.
Lastly, another theory claimed that unrestricted bacterial growth in the body generated heat and led to combustion. This would lead to death via infection long before causing any heat to generate and was thus disregarded as an SHC theory. The implausibility of these theories only acted to further the belief in the wick effect theory as the cause of SHC.
It is clear to see that SHC is not a spontaneous phenomenon. Unlike prior beliefs, people cannot simply disappear into flames. A source of heat is required to kickstart the process, and the process itself is a postmortem event, not a cause of death. Although the wick effect is scientifically valid, it is still considered the most likely explanation, rather than the real cause.
Due to its lack of spontaneity, scientists have suggested renaming SHC to better reflect what actually occurs. Alternative names include ‘isolated body combustion’ or ‘isolated central body combustion’.
