Non sembra fuori luogo la considerazione che milioni d'anni fa, in Africa, la nostra specie fosse esposta a gravissimi pericoli, rappresentati da ragni tutti molto velenosi e pericolosissimi. E' stato condotto uno studio su 252 volontari, esponendoli visivamente ad immagini computerizzate riproducenti vari soggetti, talvolta forme astratte o deformate.
La risposta alle immagini di aracnidi è sempre stata più pronta e più veloce che quella di fronte ad altre immagini fastidiose (aghi, mosche) e consistente in evidenti paura e disgusto.
Si deve considerare che - anche nel caso di sopravvivenza all'iniezione diretta del veleno - l'inabilità motoria stessa, successiva alla puntura, esponeva il nostro antenato a problemi gravissimi, tutti potenzialmente mortali.
Da qui, l'importanza di riconoscere il nemico nascosto e mimetizzato ('pareidolia') - come è spesso il ragno - e il movimento d'allontanamento rapido dovuto al moto di repulsione 'istintiva': una reazione guadagnata in alcuni milioni di anni di convivenza con gli aracnidi..
Fear of spiders written in our DNA
Fear of spiders is a survival trait written into our DNA, researchers have discovered.
Dating back hundreds of thousands of years, the instinct to avoid arachnids developed as an evolutionary response to a dangerous threat, the academics suggest.
Researchers say a fear of spiders is a survival trait written into our DNA and dates back thousands of years
[Credit: Alamy]
It could mean that arachnophobia, one of the most crippling of phobias, represents a finely tuned survival instinct.
And it could date back to early human evolution in Africa, where spiders with very strong venom have existed millions of years ago.
Study leader Joshua New, of Columbia University in New York, said: ‘A number of spider species with potent, vertebrate specific venoms populated Africa long before hominoids and have co-existed there for tens of millions of years.
‘Humans were at perennial, unpredictable and significant risk of encountering highly venomous spiders in their ancestral environments.
‘Even when not fatal, a black widow spider bite in the ancestral world could leave one incapacitated for days or even weeks, terribly exposed to dangers,’ he told the Sunday Times.
The research team carried out an experiment in which 252 volunteers were asked to study computer screens containing abstract shapes and data.
Their reactions to images of spiders were very fast, even if their shape was distorted, when compared to much more clear images of other objects known induce disgust or fear, such as needles and flies.
The researchers point out that spiders are often small dark creatures that tend to hide in recesses and are hard to spot.
Dr New said: ‘Detection, therefore, is the critical arbiter of success in such encounters — any improvements to the sensitivity, vigilance, reliability and speed of faculties for their detection would have been of significant selective advantage.’
The study has been published in the journal of Evolution and Human Behavior.
Author: Ben Spencer
Source: Daily Mail Online [April 05, 2015]
