Near-death experiences might be an unlikely survival strategy, study claims

To go to the edge of death and back again is a journey few people take so much remains a mystery about near-death experiences.

Now new research suggests that some near-death experiences may be related to an animalistic survival strategy called thanatosis, where creatures and critters play dead or feign death to evade threatening predators.

"In this paper, we build a line of evidence suggesting that thanatosis is the evolutionary foundation of near-death experiences and that their shared biological purpose is the benefit of survival," says neurologist Steven Laureys from the University of Liege in Belgium.

After a brush with death, some people describe it as an out-of-body experience, having a warped sense of time, speedy thoughts, hallucinations, seeing bright lights, or even feeling a sense of peace and acceptance.

These near-death experiences typically occur when someone is close to death, in a life-threatening situation, or experiencing some intense physical or emotional pain or stress, possibly during a heart attack or wildlife encounter.

Some of the brain mechanisms that have been linked to near-death experiences are not unlike those underpinning thanatosis, the researchers behind this paper claim, which led them to explore if the two are somehow related.

"We think that the cerebral mechanisms behind near-death experiences have evolved from thanatosis because they offer a survival benefit during predatory attacks," the researchers write in their paper.

In previous research, from the same team of neurologists, up to 1 in 10 people reported having a near-death experience. However, other data suggest it could be anywhere between 4 and 15 percent.

The question, for this group and their systematic evolutionary investigation, was how many (if any) near-death experiences typically involve a predatory threat and possibly resemble thanatosis, a survival strategy of last resort.

There are several approaches – but no definitive explanations yet – attempting to make sense of strange, sensory near-death experiences; some are scientific, many are religious, and others have cultural connotations.

From a scientific perspective, near-death experiences (NDEs) could be triggered by anesthetic drugs, a lack of oxygen, dying brain cells, or endorphins, which are released in times of high stress – but none of these explain the full array of people's experiences.

As for thanatosis in humans, it has been described as a possible defense mechanism that kicks in during traumatic events, such as sexual assault or gun violence.

People might have a "sudden onset of immobility" and "enter a state of dissociation which helps them to cope with the situation," the researchers suggest, which sounds something like the dissociation reported in some near-death experiences.

Surveying the literature, the team found 32 published papers describing thanatosis across the animal kingdom – in insects and reptiles to birds and mammals (but not great apes).

"This universality suggests that near-death experiences may have a biological origin and purpose," writes the team, led by neurologist Costanza Peinkhofer from Copenhagen University Hospital.

Next, Peinkhofer and colleagues analyzed cases of near-death experiences in a database featuring testimonies from some 630 people.

The researchers were particularly interested in cases where a near-death experience had involved some predatory threat, such as an oncoming car in a traffic accident or a wild animal – to see if there might be some kind of thanatosis-like survival benefit associated with the quick-fire thoughts, time warps or other experiences that people who come back from the brink of death so often describe.

But these types of near-death experiences, triggered by a predator-like threat, were represented in only a small fraction of the cases in the database – about 90 cases or roughly 14 percent – which means making any firm conclusions is rather difficult.

Most cases were actually related to cardiac arrests, anesthesia or surgery, and also fainting.

Looking more widely, the team also found a handful of near-death experiences, documented in news articles and historical sources, such as this person who was attacked by a grizzly bear:

"When I decided that the only option was to play dead, I just went limp. Like a rag doll, didn't move a muscle, didn't move an eyelid," they wrote. "You can disassociate yourself from what's going on…"

Peinkhofer and colleagues posit that near-death experiences such as this one hint at an overlap between some near-death experiences and thanatosis, which is also known as tonic immobility.

"We hypothesize that the greater sophistication of the human brain and the acquisition of language enabled humans to record and share their experiences in detail with others, thereby transforming these events from relatively uniform tonic immobility into the rich perceptions that form near-death experiences," the team concludes.

So what have we learned? Although an evolutionary link between playing dead for safety's sake and near-death experiences could be possible, it seems somewhat tenuous at this stage, based on this study, which pieces together various published literature and data sources.

It also wouldn't apply to any and all situations where someone has a brush with death, but rather limited to situations where people feel threatened by a 'predator', the researchers say.

"This pertains only to a minority of life-threatening situations," they write. "Since humans no longer have natural enemies, in most life-threatening situations (or situations that are perceived as such) NDEs are unlikely to have a specific biological purpose or their benefit might be less obvious.

Which leaves plenty of room for mystery.

The study was published in Brain Communications.

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