If we could eradicate disgust, would global warfare disappear? That is the intriguing thesis of Marc Hauser, Professor of Psychology at Harvard University and contributor to Edge (www.edge.org), a discussion forum for some of the world’s leading scientists.

Every year, Edge contributors are asked to consider an open-ended question. In his response to this year’s poser — What are you optimistic about, and why? — Hauser suggests that science may be able to rid the world of prejudices such as racism and sexism. These “isms” are fuelled not only by the perception of difference, but by the systematic denigration of others.

Pivotal to this process is disgust. Some aspects of this emotion are common to all cultures (an aversion to faeces and urine) but others are culture-specific. The agreeability of consuming sheeps’ eyeballs or chicken’s feet, for example, varies between countries.

Hauser calls disgust a “mischievous emotion”, stretching beyond the purpose for which it originally evolved (most probably to keep us away from disease-carrying substances) and leaking into other arenas, such as the construction of social hierarchies. Look at the Indian caste system — the Dalits, or untouchables, perform the dirtiest work (such as handling dead animals or human excrement), live apart from polite society and, in some rural regions, are still banned from temples.

One ritual of human warfare, Hauser notes, is to reduce a foe to the status of vermin, parasite or filth. It is extraordinary today to think that Hitler was able to equate Jews with pestilence to such an extent that he could murder six million of them.

But disgust is not on everyone’s emotional radar. Sufferers of Huntington’s disease (HD), an incurable genetic disorder that gradually destroys motor control, cannot recognise it in others. When shown photographs of “disgusted” people, Huntington’s patients most often interpret the expression as anger. And this inability to register disgust is evident in those with presymptomatic HD. Hauser suggests that “modern molecular techniques will one day find a way to cure Huntington’s, but along the way, work out a method to crank down or turn off our disgust response, while preserving our motor systems”.

Laudable though this may be, I find it very hard to imagine a world without disgust. What repels can also fascinate (say, the Suffolk murders). Disgust sets boundaries that can be exhilarating or liberating to cross (fraternity initiation rites). The path from birth to death, in fact, brings a catalogue of disgust — we defecate, fornicate, decay and then rot.

And disgust is, of course, entwined with sex and love. William Miller, author of The Anatomy of Disgust, wrote that love, whether sexual or non-sexual, “involves a notable and non-trivial suspension of some, if not all, rules of disgust”. Without that symbolic breach of decorum, would we truly know the nature of love?

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