Scavenger insects sense chemical signals emanating from a dead body several kilometers away. Therefore, wherever the corpse is, after some time, organisms involved in decomposition (necrophages) appear on it. Flies find buried bodies even at a depth of two meters underground. The whole secret lies in the volatile substance putrescine, which creates the terrifying smell of rotting meat, also called the “smell of death.” But it seems that not only necrophages are able to react to this substance. One study showed that the “smell of death” affects the human psyche and changes behavior even if the person himself does not feel it or identify it.
«The smell of death» causes anxiety and changes a person’s behavior. Source: minutkoclinic.com
How the “smell of death” affects a person
It is not difficult to guess why some insects are susceptible to putrescine – it allows them to find food at a great distance. Let us recall that necrophagous insects take direct part in the process of body decomposition. For grave flies, which are able to penetrate the ground to a great depth, corpses also serve as a place where they lay eggs.
But why are people able to detect the smell of a decomposing body so subtly and react to it, even if they themselves do not notice it? Scientists have suggested that this smell serves as an alarm signal for us. Several studies were conducted to verify this. The most revealing was the work of 2015, during which the authors conducted several experiments at once.
The “smell of death” is the name given to the volatile substance putrescine, secreted by a dead body. Photo source: zebra-tv.ru
First of all, the scientists checked how putrescine affects human vigilance. For this, the participants of the experiment were divided into three groups, each of which was given water, ammonia or putrescine to smell. Then all the participants of the experiment were given a computer reaction test.
The participants in the experiment were also asked to walk 80 meters after sniffing one of the three substances. The authors of the experiment measured the time it took the volunteers to walk this distance. In addition, several more experiments were conducted in a similar manner, during which they tested the volunteers' defensive behavior, thoughts of escape, and some other reactions.
It should be noted that during all the experiments, the smell of putrescine was so weak that the volunteers did not notice it. However, in all cases, putrescine changed people's behavior – the participants in the experiment were more alert, showed a high reaction speed, began to walk faster and generally sought to escape. In addition, the volunteers demonstrated more hostility. The authors of the study report this in the publication Frontiers in Psychology.
The smell of a corpse activates the “fight or flight” response. Photo source: hyderabadmail.com
Why the smell of a corpse changes people's behavior
The study actually confirmed the scientists' assumption – putrescine really does cause anxiety in people. To be more precise, this smell most likely activates the “fight or flight” system, which can save life in a dangerous situation. However, scientists do not know what kind of threat the “smell of death” warns about, and why this reaction is activated at all.
However, it is safe to say that a peculiar response to the smell of a decomposing body arose in the course of evolution in our ancestors. There are different assumptions about this. For example, the smell of a corpse made it clear to our ancestors that they had entered the territory of a dangerous predator, so it was necessary to leave it as quickly as possible.
In addition, the cadaveric smell could warn of a bacteriological threat. After all, decomposing meat contains cadaveric poison and dangerous bacteria. Thus, putrescine could signal our ancestors that they should stay away from the corpse. The researchers themselves assume that both options are true. Therefore, even a barely perceptible “smell of death” causes anxiety, wariness and a desire to run away.
Unpleasant smells still protect us from various dangers. Photo source: balashover.ru
However, unpleasant odors that signal a bacteriological threat usually cause disgust or even vomiting, but not the desire to flee. For example, spoiled food in the refrigerator does not activate alertness and the “fight or flight” response. Therefore, it can be assumed that the “smell of death” is primarily associated with the danger posed by predators. To accurately answer this question, the authors plan to conduct additional research in this area.
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But, in any case, there is no doubt that the perception of smells helped our ancestors survive in a dangerous environment. Therefore, all people, regardless of race and culture, are disgusted by the same smells. There are also smells that absolutely all people find pleasant. For example, one study showed that absolutely all people like the smell of vanilla. You can read more about this at the link.