Something strange is happening to our sense of smell. More and more people find it difficult to cope with ordinary odours. In summer, we suffer from hay fever and a host of other allergies. One in five babies is born with asthma, and with immune systems so weak that almost any kind of smell can trigger an allergic response. Anosmia, the medical term for the loss or impairment of the sense of smell, has become common. Are we in danger of evolving our sense of smell out of existence?
In certain parts of North Ameri-ca, smells have become so problematic that they have been outlawed from work and public places. In Halifax, Nova Scotia, a "no-scent encouragement programme" is strictly implemented: people who wear perfume, deodorants or any other kind of fragrance that can cause allergic reactions in passers-by are dealt with speedily. Many US firms have a smell policy declaring that "employees will wear no perfume or cologne during business hours". The movement for "fragrance-free zones" is gaining ground in California, Texas and other states. Environmentalists are threatening to file personal injury class-action suits against perfume, deodorant and other industries specialising in the production of pong.
There is a sensible reason for this apparently senseless action. A growing number of people (between 15 and 30 per cent of the US population) suffer from the new disorder of multiple chemical sensitivity (MCS). They have severe reactions to scented products - reactions that can include headaches, nausea, dizziness, memory loss, breathing difficulties, even death. Where America leads, we follow. It is only a matter of a few years before MCS, and smell policies, become a major issue in Britain.
Why are our noses getting so sensitive? The answer lies in the way we have banished natural odours from our daily lives so that we now, for the most part, smell an artificially created, chemically enhanced, poisonous stench. The smells that surround us affect our well-being throughout our lives. And we have surrounded ourselves with the stench of traffic fumes, the whiff of tarmac, the stink of industrial effluents. But that's only part of the problem. Inside our homes, in enclosed environments such as the motor car, we use a plethora of artificial air-fresheners whose fragrance makes ordinary breathing hazardous to health. When did you last get into a taxi or a minicab that was not a cornucopia of chemically simulated smells?
Our houses have become paradises of artificial reek. Just look around you. Air-fresheners, plug-in air purifiers, electrical ionisers, chemically enhanced pot pourri, pongy soaps, smelly shampoos - the list of household items with artificially enhanced smells is endless. When did we discover the need for coathangers filled with lavender? Sometime, I suppose, after the arrival of the roll-on underarm deodorant and all the other noxious personal hygiene paraphernalia on which we spend so much of our disposable income. We have developed a fetish for the hint of "fresh pine" included in any number of household cleaning products. Having arranged for the rapid disappearance of actual pine forests, we imagine ourselves strolling through forest glades as we visit our loos in the heart of a sprawling conurbation. Or maybe your chosen household cleaning fragrance is lemon, so that you get the whiff of a distant Mediterranean hillside as you mop cat pee from your non-slip terracotta kitchen tiles. It is hardly surprising that our nasal odorant receptors cannot cope with this chemically enhanced overload.
Smell is inherently evocative. That is why manufacturers spend millions putting scents into their products, and why advertisers want to get in on the act, too. Soon, artificial smells of camphor, musk, peppermint and exotic spices will be streaming from our computer terminals. Smells have been digitised, and they can now be attached to your e-mail, Word document, interactive game or the music you download from the internet. There will be no escape from the world of the artificial odour.
There is a pattern to all this. The rule is that we must ingest through our nostrils only artificially simulated natural fragrances of a certain ilk. We rigorously avoid such natural fragrances as might, in the normal course of our lives, mingle with our activities.
Indeed, western culture has developed a deep aversion to natural smells, including the odours of human beings. There is something shameful, we teach our children, about the smell of human sweat or of our normal bodily discharges. Only cats and dogs use smell to locate their food, recognise each other and perform other social functions. Civilised behaviour requires that we be totally free of natural smell.
I am reminded of my experience in a small European hotel. The modest pension had a toilet that resembled a throne room, approached up an impressive flight of steps. Every vantage point in this small, airless chamber was occupied by some form of artificial device, spewing forth powerful, chemically enhanced smells. So overpowering was the effect that one emerged doubly relieved - not merely of bodily waste, but also of the inner lining of one's lungs. As I lingered in the vicinity, gasping for breath, I overheard a group of nice British ladies who were next in line to use the facilities. One by one, they diced with suffocation, warning the next in line to hold her breath and be quick. The last in line, obviously "a character", finally emerged and announced, without hesitation: "Give me the good honest smell of shit any day!"
Ah, the candid smell of shit! Not for nothing is "shit" considered to be a taboo word; and "bullshit" has become one of the most derogatory words in our language. Our entire history - indeed, the course of human evolution - has been marked by efforts to escape the smell of shit. Or, at least, this is what we are told by the emerging, hip and cutting-edge discipline of evolutionary psychology.
In Leda Cosmides and John Tooby's Evolutionary Psychology: a primer, we learn that our neural circuits were designed by natural selection to solve problems that our ancestors faced during the evolutionary history of our species. And what was the most important problem confronting our Stone Age ancestors? It seems that, out on the African savannah, our evolving species had to acquire "appropriate" behaviour - they had to learn how to get away from the smell of faeces. "Appropriate", we are told, means different things to different organisms. For example, the dung-fly is hugely attracted, not to say aroused, by smelling faeces and will make a beeline, or dung-fly dive, to the steaming pile to mate and lay her eggs. But for you, write Cosmides and Tooby, bullshit is "not food", or "a good place to raise children" or arrange a date. "Because a pile of dung is a source of contagious diseases for a human being, appropriate behaviour for you is to move away from the source of the smell."
So there you have it. The latest research into the origin and development of humanity confirms that the good honest smell of shit was as inappropriate to our ancestors as it is to their latter-day descendants running a European pension. It is not only in our genes; it is imprinted in our neural circuitry. To be human is to avoid the smells of human bodily functions; thus we become aware that we are not dung-flies, but rational, sentient life forms.
This argument, like much of evolutionary psychology, may be described as nothing more than bovine excreta. In non-western cultures, exactly the opposite is true. Far from wrinkling its nose with universal disgust, a large part of the human race regards dung as a vital economic resource to be gathered and utilised with care, if not reverence. The villages of India are fuelled by cattle dung; the family meal is as likely as not to be cooked on fires fed by this gift of Mother Cow. The earliest recorded annals of ancient China show that the regular collection of night-soil for fertiliser was a source of civic organisation and pride. Many villages in Africa are composed of mud huts plastered with a fine coating of animal dung, which, being naturally fibrous, makes an excellent form of cement (you remember the old adage about no bricks without straw?). Not so long ago in Britain, entire urban populations hotfooted it with bucket and shovel to collect horse manure to nurture rhubarb patches, city gardens and allotments.
When I worked as a development journalist, I travelled extensively through India and China, looking at the design of and testing biomass converters that generated electricity from cattle dung and human bodily waste. They were supposed to solve the energy problems of developing countries - and would have done if someone had bothered to get the technology right.
History without the honest smell of shit is an impossible concept. As Patrick Suskind showed so brilliantly in his novel Perfume (1986), the cities of Europe, before the invention of squeamishness, were alive with all variety of natural smells. Streets ran with human waste, rivers were civic cesspools, and pisspots were emptied out of upstairs windows. Even the best French perfume needed traces of faeces to make it distinctive. It was the rich pattern of urban living, rich in smell.
I am not advocating mucky living. Cleanliness and natural odours are not mutually exclusive. It is hardly more than a hundred years ago that Europe discovered the benefits of personal hygiene. In contrast, public baths were common in Baghdad and Damascus more than 1,000 years ago. Indeed, millennia ago, daily washing and bathing became a prerequisite of faith in both Islam and Hinduism. The most sophisticated sewage system in the world, built by the Ottomans in the 14th century, can still be found under the hills of Istanbul.
So cleanliness is not a western discovery, even though it was the Victorians' passion for the water closet and their building of municipal sewage systems that did more to improve the survival rates of the industrial working class than anything else known to humanity. The water closet and the sewage drains ended the scourges of cholera, typhoid and dysentery. But the western world, cultural neophyte to cleanliness, has become paranoid and totally unbalanced on the subject. It now wants to banish natural odours from the planet altogether and replace them with simulated, artificial varieties.
The consequences of continuous avoidance of natural smells are quite devastating. An average human being has the capability to recognise more than 10,000 separate odours. But overexposure to manufactured pongs leaves most of us unable to recognise more than a dozen smells. Something smells like roses, like pine, like lemon, like burnt wood, like sweat, like bad eggs, like ammonia, like shit. That's about it. Even our vocabulary for describing smells is rather limited.
Quite apart from losing our sense of smell, we are doing irreparable damage to our children. Our overhygienic homes and sterile lives, free of natural odours, fail to expose children to bacteria that kick-start the immune system and enhance its protective abilities. This is why our children are increasingly unable to fight off allergens, and why asthma has become a curse of modern times. As it happens, there is another connection with shit here, because most of these bacteria flourish in the bowel, and the latest cure for preventing asthma and other allergies involves feeding such bacteria to, or injecting them in, babies a few weeks old.
Avoidance of natural smell is also undermining our humanity. Before artificially induced hygiene became a fetish, the aristocracy and nobility might have wandered around with their nosegays at their nostrils and used high-priced spices to make pomanders - but they stank like everyone else. Stink was a shared, universal inheritance.
Now, only the poor stink. This point was impressed on my sizeable nasal cavity the other day on the London Underground. I was sharing a carriage with sundry aromatically arrayed Londoners, when a homeless dosser walked in. He stank, he reeked, he was fetid and ripe - and we all turned away and attempted to envelop ourselves in our costly, shop-bought personal odours as we tried not to look at him. A few passengers changed carriages. The odour of poverty is indeed the most noxious - it prevents us from looking the poor straight in the eye. If you smell like shit, you shouldn't be surprised at being treated, as the word itself suggests, as a contemptible, worthless person, beyond the pale of humanity.
So now only the poor know what our noses were really made for. In the housing estates of Britain, in the black ghettos of America, in the shanty towns of Asia, in the villages of Africa, the scent of poverty is the most evocative odour of them all. Smell is a class issue. It reminds us of the existence of a premodern, unreconstructed waft of humanity in our middle-class, hygienically wrapped, postmodern world of artificial odours. Only the poor know the truth - that our olfactory tolerances are a measure of our atrophying human compassion and concern.
So, if you want to save your humanity, save your children, save the world, then save your sense of smell. Go out and smell some real bullshit. It would do you a world of good.
The complete text of Evolutionary Psychology: a primer by Leda Cosmides and John Tooby is available from www.psych.ucsb.edu/research/cep/primer.html. Information about digital smells can be found at www.digiscents.com. Ziauddin Sardar's The Consumption of Kuala Lumpur is newly published by Reaktion Books at £17.95