On May 29, 1953, Tenzing Norgay and Edmund Hillary took the last few decisive steps up Mount Everest, and became the first known humans to reach the summit of the highest mountain on Earth. For fifty years their story has captured the popular imagination, and inspired generations of mountaineers, adventurers and ordinary people looking to applaud the stamina of man and marvel at his determination. But over this time, scientists have begun deconstructing why a person might take themselves out of their ordinary environment and perform such a feat. The golden anniversary of that first successful ascent is upon us, so let's sit back in our warm comfortable homes away from the wilds of the Himalayas and examine some of the neurological events that motivate the human spirit.
Mountain climbing is but one of the many extreme sports branded by the more cautious amongst us as reckless behaviour. As time goes by, and technologies evolve, the risk becomes more calculated, but there are still many dangers on an Everest expedition over which climbers have little control, and nature can still easily outwit the physiology of even the best equipped adventurers. Bad weather conditions, for example, can cause frostbite, whilst the decreased barometric pressures high up on Everest can lead to altitude sickness. There are also emotional difficulties to contend with including homesickness, fear, and the mental torment of being uncertain whether your credit card bill has been paid on time (note, this was not a plug for egg.com, for those who have seen the TV advertisement) !
Despite all the danger - or perhaps because of it - mountain climbing and other extreme sports have the admiration of amateurs, and the addiction of the die-hard. Behavioural geneticists, on the other hand, prefer you to believe that all the enthusiasm and hype boils down to a simple case of dopamine biology. Scientists have shown that genes that control sensitivity of our nerve cells to the neurotransmitter dopamine, one of the brain's pleasure chemicals, are responsible for a number of personality traits and psychiatric disorders. When dopamine is released by neurones in the 'reward centre' of the brain, it generates a feeling of pleasure and well-being as well as increasing alertness. The heart takes a beating as well; dopamine increases pulse rate and cardiac contractility, poising the body for action. Dopamine and sensations of reward are thought to have evolved to reinforce the motivation for performance of beneficial activities such as eating and drinking. For instance, when hunger is satiated, dopamine is released, helping to promote the pattern of behaviour that led to this beneficial outcome.
Adventures make a person feel more alive - they provide pleasure and satisfaction and increase awareness and perceptivity. The finding that dopamine is released during a new experience, and is responsible for these sensations, therefore comes as no surprise. Remarkably though, pain can also cause release of dopamine, so it makes sense that mountain climbing is an enjoyable activity; the climber experiences extraordinary terrain and pushes himself physically to the point of agony. Dopamine is released and everyone has fun!
The average person likes an average amount of novelty in his or her life. But some people seem to be more adventurous and continuously pursue diversity, even if their activities involve dangers best left untested. Individuals like this tend to lag if they are not constantly stimulated, and they begin to feel inert and depressed. Several landmark studies found that this 'novelty seeking' personality type is linked to a gene called D4DR which encodes a dopamine receptor, a structure found on the surface of nerve cells which enables them to detect the presence of dopamine. Critically, the length of the D4DR protein affects how strongly cells react to dopamine. People with a long version (genetically known as a 'polymorphism') of D4DR are more sensitive to fluctuations in dopamine levels than the more common short version. They feel low at levels of dopamine that suffice to stabilise the mood of the average person, but when dopamine levels are increased, they sense thrills more intensely than comparatively staid folk, and it is this 'hit' which leaves them craving new highs. Indeed, certain drugs such as cocaine work by simulating the action of dopamine on the brain and so, not surprisingly, research has it has shown that people with longer versions of the D4DR gene are more likely to become addicted to drugs, although these findings are controversial. Presumably, these individuals are 'self-medicating' to correct for the mood deficit caused by their dopamine sensitivity. Nonetheless, it is important not to lose sight of the fact that hard-core drug abusers still tend to come from underprivileged groups, underlining the impact of the environment upon personality, and the need for social change.
Edmund Hillary talks about his fascination with adventure as a young boy in several interviews. He must be no stranger to the effects of dopamine release. But he also speaks about the amount of planning and organisation that goes into preparing for a major expedition. Some scientists would like to explain away the fascination with extreme sports by blaming it on an aberration of genetics. Yet, if people with a novelty-seeking personality needed a quick fix to keep their moods stable, would they really seek out a sport as drawn out as mountaineering? If their attention span lags, could they be bothered to plot and plan? Perhaps the answer lies in the magnificence of the mountains. The adventure of exploring the grandeur of Nature must endlessly re-new itself whilst the thrill of experiencing the elements that carve our world must help to maintain interest. Or perhaps the moment-to-moment strategic decisions, which are needed to make climbing physically possible, make all the planning worthwhile.