Arachnophobia! Your ancestors are to blame for your spider fear
Afraid of spiders? It's all your ancestors' fault according new research into our irrational fears.
It sounds like a dream: you're in theatre and you're the star of the show. Except that it's an operating theatre, you're the patient, and the drugs haven't knocked you out properly.
Instead you become trapped in a living nightmare: sufficiently conscious to register the incoming scalpel, but unable to scream for the surgeon to stop.
Around 140 patients each year endure "accidental awareness under general anaesthesia" (AAGA) when drugs fail to induce full unconsciousness. That represents around one in 19,000 operations, according to an audit of three million operations carried out by the Royal College of Anaesthetists, together with the Association of Anaesthetists of Great Britain and Ireland.
The true picture, however, may be worse: if, instead of relying on spontaneous reports, patients are specifically asked about whether they remember anything between the moment they go to sleep and the moment they wake up, the figure rises to one in 600 operations. That would push the number of patients affected each year into the thousands. These figures suggest that harbouring a phobia about anaesthesia awareness, as many do, is entirely reasonable.
In fact, the more we learn about our supposedly irrational fears, the more rational they seem to become. Phobias, which are extreme fears of certain objects or situations, are a persistent feature of the human psyche - and many of the most common ones are thought to serve a survival purpose.
For the past week, I have been tiptoeing around and ducking down in my front garden to access my bin cupboard, so as not to disturb the enormous spider's web strung like a silken hammock between cupboard and hedge. The wariness is cowardice rather than respect for arachnid engineering; the idea of my eight-legged lodger crawling into my hair as I dispose of the rubbish inspires an uncontrollable shiver.
Arachnophobia, which is one of the 10 most common phobias listed by Anxiety UK, is among those suspected of having an evolutionary origin. The argument goes like this: as we evolved, the humans who enjoyed the best chance of survival were those who were most attuned to threats. Poisonous spiders and snakes represented real dangers - only those who dodged them survived to pass on their genes. Our fearful ancestors thus won the battle for survival - and we inherited their brain circuitry.
Our environments, meanwhile, have changed far faster than the pace of evolution can keep up with: even though these natural threats have largely disappeared, our neurological circuitry remains pretty much prehistoric. And so, to this day, certain objects or situations - spiders, snakes, the dark, strangers - continue to stir a terror in the soul. That terror triggers physiological changes, such as sweating and an increased heart rate.
Agoraphobia, a fear of open spaces, might have been similarly protective. Others in the top 10 include hypochondria (fear of illness), social phobia (fear of social interaction, particularly of rejection or of looking like an idiot), emetophobia (fear of vomiting) and claustrophobia.
Fascinatingly, some people have a blood-injury-injection phobia, sometimes called a bodily phobia; one study found it was three times as common among women of child-bearing age than menopausal women. This higher incidence in fertile women, the scientists suggested, would be expected if this particular fear circuitry evolved for survival reasons. The surprisingly high incidence of phobias in general - affecting one in 12 people - may also point to an inheritance from our nervy ancestors.
We continue this proud tradition of fearfulness when we become parents. I have yet to meet a mother who didn't peer anxiously into the cot at night to establish that her baby was still alive. A doctor friend even used to use a feather as a respiratory diagnostic aid, to keep her nocturnal investigations brief.
It's not uncommon for new mothers to show symptoms of obsessive-compulsive disorder (OCD). According to a paper last year in the Journal of Reproductive Health, one in 10 mums showed symptoms of OCD within two weeks of birth, such as excessive bottle washing, with half of those still showing symptoms at six months.
The evolutionary hypothesis of phobia is not uncontroversial: other studies suggest we learn fear responses from our parents. Whatever the truth, we are an anxious species, often paralysed by the threats we can see and panicked by the ones we can't.
Of course, we should try to conquer our terrors: I shall bravely continue to put the rubbish out, defying the gargantuan inch-wide nemesis that has appropriated my house frontage. But, if our fears really are a hangover from evolution, we should thank our cowardly forebears for the fact that we are here at all.
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