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 've been tiptoeing around and ducking down in my front garden to access my bin cupboard in order 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 rubbish inspires an uncontrollable shiver.
Arachnophobia, which is one of the 10 most common phobias, 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 have changed far faster than the pace of evolution can keep up with: these natural threats have largely disappeared, but our neurological circuitry remains pretty much prehistoric.
To this day, certain objects or situations - spiders, snakes, the dark, strangers - continue to stir terror in the soul that 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. Some people have a blood-injury-injection phobia, sometimes called a bodily phobia.
Phobias are common, affecting one in 12 people .
According to a paper published in the Journal of Reproductive Health, one in 10 mums showed symptoms of obsessive-compulsive disorder within two weeks of birth, for example excessive bottle washing.
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 enemy 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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