Some years ago, while climbing in thin air, I met a man who wasn’t there. I had climbed solo to the mountain peak of Aconcagua in the Argentine Andes. Being fit and foolish, I had climbed too rapidly for adequate acclimatisation to occur. As I staggered down from the 6 959m summit, frostbitten, exhausted and alone, I felt the powerful sensation of being accompanied by somebody. I turned around repeatedly to look for the person, but there was nobody to be seen on the windswept slopes.
I kept descending, feeling in some strange way as if I were floating slightly above my body, my invisible companion following behind me, encouraging me to keep going. Lower down the mountain I felt stronger, and my follower disappeared as mysteriously as he has arrived.
This month sees the 50th anniversary of the first ascent of Everest, climbed with bottled oxygen. Numerous climbers attempting the feat without additional oxygen have had anomalous experiences identical to my Aconcagua hallucination.
Peter Habeler and Reinhold Messner were the first to climb Everest without oxygen in their ascent in 1978. Habler wrote that he felt as if he stepped outside himself, as if some other person were climbing Everest in his place.
Messner, climbing Everest solo without oxygen in 1980, suspected he was being accompanied on his climb by phantom helpers. He wondered if these were perhaps the ghosts of British climbers who had died on the slopes years earlier.
The British climber Frank Smythe, attempting Everest alone without oxygen in 1933, felt the presence of another climber so strongly that he caught himself turning around to share his lunch with his illusionary companion.
Many other climbers have reported these mysterious presences and sensations at extreme altitudes. Sensations of floating out of one’s body
are, of course, well documented, but are usually described by people who have near-death experiences, such as drowning or being resuscitated in a hospital.
While accounts for these experiences include yetis, ghosts or God, recent scientific neurological evidence suggests a more prosaic biological explanation.
The brain functions in a modular fashion, with different parts of the brain contributing different pieces to how we perceive and move in our environment. An area of the brain that integrates sensory input into a cohesive picture is the parietal cortex, the surface of the brain situated beneath our temples, slightly above the ears.
The integration of multiple sensations — sight, sound, bodily position sense — allows us to maintain a continuous perception of where we are in space.
For decades doctors have known that tumors and lesions in certain parts of the brain can produce the perception of a phantom doppelgänger — the powerful sense that someone is nearby. More recent experimental evidence, published in the leading scientific journal Nature last year, provided further insight. Doctors placed electrodes in the parietal cortex of a woman with severe epilepsy. Electrical stimulation in an area of the cortex known as the angular gyrus produced sensations of floating out of body.
Taken together with other prior experiments, this suggested that dysfunction in a highly specific region of the brain can produce disturbances to our self-perception of bodily position.
Disruptions of the oxygen supply to this part of the brain, such as during a near-death experience, or when climbing vigorously in the rarified air of extreme altitude, may cause loss of this integration of position sense.
Hallucinations of floating, or of a phantom presence, may arise from this disturbance.
The neurological story may not end in the parietal cortex. How we perceive this abrupt breakdown may depend on the interpretive function of a different part of the brain, known as the limbic system.
Under threatening circumstances spatial disruption may be perceived in a benign fashion, rather than as a frightening, unfamiliar experience. This might account for why mountaineers commonly describe their shadows as comforting, helpful presences in extreme conditions.
I was somewhat relieved to discover that my earlier oxygen-addled experiences were not the product of a crazed mind, but rather had a rational theoretical explanation in the fields of neurophysiology, or cognitive psychology.
This feeling was soon supplanted
by a vague disappointment that my friendly ghost, or guardian angel of high altitude, was apparently no more than a neurological short circuit.
But then I realised that a biological explanation does not preclude a benign metaphysical origin — an explanation of ”how” does not answer the question of ”why”.
Whatever the physiological details of these experiences of mountaineers at extreme altitude, why else would these helpful ghosts be wandering in the penumbral world of the edges of our perception?
Paul Firth studied medicine at the University of Cape Town and is currently an anaesthetist at the Massachusetts General Hospital in Boston