Many people across different cultures and historical contexts have reported experiencing near-death experiences. When going through such singular life-threatening episodes, it’s common to experience things such as no pain, seeing a bright light at the end of a tunnel, or detaching from one’s body and floating above it, and even flying off into space. This universality suggests that near-death experiences have some biological origin and purpose — and a new study seems to confirm this idea.

Evolution towards a bright light at the end of a tunnel

Despite several theories used to explain near-death experiences, no one’s really sure what causes them or why humans have them. Religious people believe near-death experiences provide evidence for life after death – in particular, the separation of the spirit from the body. Whereas scientific explanations for near-death experiences include depersonalization, which is a sense of being detached from your body. Scientific author Carl Sagan even suggested that the stress of death produces a remembrance of birth, suggesting the “tunnel” people see is a reimagining of the birth canal.

According to researchers at the University of Copenhagen in Denmark and the University of Liège in Belgium near-death experiences in humans may be the result of evolutionary mechanisms. Their investigations suggest that these harrowing episodes have arisen as a result of thanatosis — a defense mechanism in which animals feign their death to improve their odds of survival.

It’s widely believed that thanatosis exploited predators’ tendencies to avoid dead prey. Thanatosis is characterized by a number of different features: catalepsy, immobility with a prone but stiff posture maintained by pronounced tonic muscular activity; ‘waxy flexibility’ of the limbs, which if moved by an external force maintain the newly imposed position for long periods; and unresponsiveness to external stimuli, while remaining fully aware of the environment.

Thanatosis is of widespread occurrence in arthropods and in all classes of vertebrates, possibly including humans (hence the phrase ‘scared stiff’).

 “As a survival strategy thanatosis is probably as old as the fight-or-flight response,” Daniel Kondziella, a neurologist at the Copenhagen University Hospital, said in a statement.

The researchers found that thanatosis, or tonic immobility, occurs in insects, fish, reptiles, birds, and mammals. Their investigations also showed that humans can experience both thanatosis and near-death experiences when threatened by an imminent life-threatening attack such as an encounter with a grizzly bear, going through a severe traffic accident, or an assault from another human.

 “We show that the phenomenology and the effects of thanatosis and near-death experiences overlap,” said Charlotte Martial, a neuropsychologist from the Coma Science Group at the University of Liège.

Kondziella and Martial conclude that the acquisition of language caused humans to transform death-feigning into the much more elaborate and rich perceptions that characterize near-death experiences, which can extend to non-predatory situations. For instance, about one in ten patients with cardiac arrest in a hospital setting undergo such an episode. 

“Of note, the proposed cerebral mechanisms behind death-feigning are not unlike those that have been suggested to induce near-death experiences, including intrusion of rapid eye movement sleep into wakefulness,” Daniel Kondziella explains.

“This further strengthens the idea that evolutionary mechanisms are an important piece of information needed to develop a complete biological framework for near-death experiences.”

The notion that near-death experiences are the product of an inherent biological need to survive makes sense. However, this is far from the last word on the subject. Near-death experiences are not readily amenable to well-controlled laboratory experimentation, which greatly limits research, although this may change perhaps using pharmacological means.

The findings were reported in the journal Brain Communications.