Send Doris a message she cannot ignore: John Emsley sniffs out the secrets of androstenone, and the fragrant attractions on which we spend pounds 400m a year

Christmas is traditionally the time of tantalising aromas: roasting turkey, warm mince pies, smouldering Chanel No 5 and hot Jazz. These two were the best selling brands of perfume for women and men last Christmas. Among the 500 or so perfumes for women, Chanel, Anas Anas and Opium are the top three. Men's leading brands are Jazz, Kouros and Aramis, but they also have more than 300 to choose from.

Smell is the human sense we use least. It relies on our detecting individual molecules as we breathe, which we do with receptors on millions of fine hairs, called cilia, in the upper nasal cavity. Perfume molecules fit the receptors on the cilia and trigger pleasurable responses in our brain. To achieve this effect, the British spend pounds 400m a year, mostly at Christmas.

The profits on perfumes are high because the content of the product is more than 80 per cent alcohol, a chemical that industry makes very cheaply. Aftershaves and colognes may be 95 per cent alcohol and water.

Human skin produces its own smells, but we may find them offensive and some are more powerful than we imagine. When a 15-stone pig living in Gloucestershire took a fancy to a newspaper boy last month and cornered him in a telephone box, it was only responding to molecules he was giving off.

Little did he realise it, but he was sending Doris a message she could not ignore. The auxiliary glands in his armpits were releasing androstenone, which is a sex-attractant for the wild boar. In his book The Scented Ape, Michael Stoddart, of the University of Tasmania, discusses whether it could also be a human sex-attractant. Men give off much more of this than women and, curiously, the amount a man gives off reaches a maximum at this time of year. However, Professor Stoddart is doubtful of its potency because it has a weak smell, and in a concentrated form some women even find its aroma off-putting. Most of us use perfumes to make ourselves smell better.

Perfumers can be seen at work on the wall paintings of Egyptian tombs of 1,400 BC, but the perfume industry as we know it began in the Middle Ages at Grasse in Provence, southern France, where the climate and soil were ideal for growing plants from which the fragrant essences were extracted.

The traditional Grasse way of extracting the essential oils from flowers was to place them between layers of pork or beef fat, which absorbed the fragrant oil - a process known as enfleurage.

This method was superseded by steam distillation or solvent extraction, but nowadays chemical manufacture is more important. The synthesis of fragrance and flavour molecules began in the 1840s, when aromas such as cinnamon were first extracted and manufactured. However, it was the success of Chanel No 5, introduced in 1921, that gave the synthetic materials their big breakthrough. This was the first perfume to use both natural and man-made components.

Chemists can make exact copies of natural aroma molecules or modify them to produce other fragrances. Not only that, but synthetic fragrances are better than natural ones because they are chemically more stable.

'A considerable number of fragrance ingredients are man- made,' says Dr Charles Sell, head of organic chemistry at Quest International of Ashford, Kent, one of the world's leading fragrance manufacturers. 'The new products may have odours not found in nature, although they are often described by perfumers in terms of known scents.'

People put on scent to send a message. The warmth of our bodies causes the perfume to evaporate and its molecules register on sensors in the noses of those around. A perfume can communicate a message we may be afraid to put into words: at its simplest it says 'come closer', but it may be saying something much more suggestive.

There are hundreds of molecules in natural fragrances. Some are very volatile, the so-called top notes, and others less so, the middle and base notes. The deeper we get, the more subtle and suggestive is the message. A typical top-note will be instantly recognised as fresh and pleasant, such as citrus fruit or crushed leaves, while middle notes are more floral, including the heavy scents of jasmine, lilies and orchids.

The base notes hint of leather, resin, moss, earth, fragrant woods such as cedar or sandal, and even smells that we associate with intimacy. The deepest notes we may not even be aware of, but they are there and carry the most primitive messages of all. These chemicals hint of urine, blood, semen, and even excrement.

The perfume I buy my wife is Chloe, by the perfume house of Lagerfeld. The trade manual Fragrance Guide to Feminine Notes does not reveal the exact recipes of this perfume, which of course is a trade secret, but it does reveal the components. Chloe has a 'fruity green' top note of coconut, bergamot and peach, 'exotic floral' middle note of tuberose, jasmine and hyacinth, and 'feminine sensual' base note of musk, moss, sandal and cedar. All is revealed.

So where do the deepest notes of all come from? Not surprisingly they originate from the sex glands and excretory organs of animals. The chief ones are musk, civet and ambergris. Musk comes from the Himalayan musk deer, civet from the Ethiopian cat of that name, and ambergris is an intestinal secretion that is vomited up by whales and is found on beaches in lumps the size of footballs.

The most potent is musk. In its raw state this smells like a mixture of urine and animal dung; collectors used to plug their noses as they gathered it. Musk is a powerful sex-attractant for female deer, produced by the male in a pouch the size of a walnut at the base of the penis. It also contains androstenone. Humans find musk alluring when it is diluted and put into perfumes. Chemists have identified several components of musk. One, muscone, is now made in the laboratory and is the synthetic material used in modern perfumes.

The civet cat of North Africa and Ethiopia also secretes a fluid that humans find sensuous to smell. Both male and female civets excrete a white fluid into an anal sac, and they used to be kept in captivity just for this reason. The chief aroma constituent is civetone, which consists of 17 carbon atoms in a ring, to one of which an oxygen atom is attached. This substance has a floral and musky odour and has been used in perfumes for more than 2,000 years - Cleopatra was fond of it. Artificial civet is now made in the laboratory.

Perfumers have about 4,000 molecules to choose from when they design a perfume. The composition of a new scent is still more an art than a science, and is the work of a team referred to as les grands nez. It is these clever fragrance designers who make the modern Christmas morning such a celebration of the chemist's art.

Dr John Emsley is science writer in residence, department of chemistry, Imperial College, London.

(Photograph omitted)

Sport
Laura Trott with her gold
Commonwealth GamesJust 48 hours earlier cyclist was under the care of a doctor
Life and Style
Upright, everything’s all right (to a point): remaining on one’s feet has its health benefits – though in moderation
HealthIf sitting is bad for your health, what happens when you stay on your feet for a whole month?
Arts and Entertainment
Peter Griffin holds forth in The Simpsons Family Guy crossover episode
arts + ents
News
Orville and Keith Harris. He covered up his condition by getting people to read out scripts to him
People
PROMOTED VIDEO
Sport
France striker Loic Remy
sportThe QPR striker flew to Boston earlier in the week to complete deal
Arts and Entertainment
Gal Gadot as Wonder Woman
arts + entsFilmmaker posted a picture of Israeli actress Gal Gadot on Twitter
Sport
Vincenzo Nibali rides into Paris on the final stage of the 2014 Tour de France
Tour de FranceVincenzo Nibali is first Italian winner since Marco Pantani in 1998
News
Bryan had a bracelet given to him by his late father stolen during the raid
people
Arts and Entertainment
Chris Pratt stars in Guardians of the Galaxy
arts + ents
Arts and Entertainment
Pedro Pascal gives a weird look at the camera in the blooper reel
arts + entsPrince Oberyn nearly sets himself on fire with a flaming torch
News
Danny Nickerson, 6, has received 15,000 cards and presents from well-wishers around the world
newsDanny loves to see his name on paper, so his mother put out a request for cards - it went viral
Arts and Entertainment
Zoe Saldana stars in this summer's big hope Guardians of the Galaxy
filmHollywood's summer blockbusters are no longer money-spinners
Sport
Red Bull Racing's Australian driver Daniel Ricciardo (C) celebrates with Scuderia Ferrari's Spanish driver Fernando Alonso (L) and Mercedes' British driver Lewis Hamilton
sport
Arts and Entertainment
comedy
Arts and Entertainment
Public vote: Art Everywhere poster in a bus shelter featuring John Hoyland
art
Arts and Entertainment
Judd Apatow’s make-it-up-as-you-go-along approach is ideal for comedies about stoners and slackers slouching towards adulthood
filmComedy was dominated by the romcom at its most insufferable
Sport
Tour de France competitor Bartosz Huzarski’s legs have highlighted the gruelling nature of the race, after he posted a picture on Facebook showing extremely prominent veins stretching from his feet and all the way up his legs
Commonwealth Games
Life and Style
Elle Kaye demonstrates the art of taxidermy
food + drinkFood revolution taken a step further in new ‘edible taxidermy’ class
News
A rub on the tummy sprang Casey back to life
video
Sport
Halsall broke her personal best in the 50m butterfly
Commonwealth GamesEnglish swimmer is reborn after disastrous time at London 2012
Arts and Entertainment
O'Shaughnessy pictured at the Unicorn Theatre in London
tvFiona O'Shaughnessy explains where she ends and her strange and wonderful character begins
News
ebookA unique anthology of reporting and analysis of a crucial period of history
Life and Style
Workers in Seattle are paid 100 times as much as workers in Bangladesh
fashionSeattle company lets customers create their own clothes, then click 'buy' and wait for delivery
Arts and Entertainment
Red Bastard: Where self-realisation is delivered through monstrous clowning and audience interaction
comedy
Arts and Entertainment
booksForget the Man Booker longlist, Literary Editor Katy Guest offers her alternative picks
Voices
The Express offices in the 1930s when writers (such as Orwell) were paid around £2 weekly
voicesWebsites offering your ebooks for nothing is only the latest disrespect the modern writer is subjected to, says DJ Taylor
Life and Style
A cut above: Katy Guest at The Ginger Pig
food + drinkThe Ginger Pig's hands-on approach to primary cuts
Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Data Analyst

£30000 per annum: Ashdown Group: A highly reputable software house is looking ...

Application Support Analyst / Junior SQL Server DBA

£40000 - £45000 per annum: Ashdown Group: An established professional services...

Commercial Litigation

Highly Attractive Salary: Austen Lloyd: CITY - SENIOR COMMERCIAL LITIGATION SO...

BI Developer - Sheffield - £35,000 ~ £40,000 DOE

£35000 - £40000 per annum + competitive: Progressive Recruitment: My client is...

Day In a Page

A new Russian revolution: Cracks start to appear in Putin’s Kremlin power bloc

A new Russian revolution

Cracks start to appear in Putin’s Kremlin power bloc
Eugene de Kock: Apartheid’s sadistic killer that his country cannot forgive

Apartheid’s sadistic killer that his country cannot forgive

The debate rages in South Africa over whether Eugene de Kock should ever be released from jail
Standing my ground: If sitting is bad for your health, what happens when you stay on your feet for a whole month?

Standing my ground

If sitting is bad for your health, what happens when you stay on your feet for a whole month?
Commonwealth Games 2014: Dai Greene prays for chance to rebuild after injury agony

Greene prays for chance to rebuild after injury agony

Welsh hurdler was World, European and Commonwealth champion, but then the injuries crept in
Israel-Gaza conflict: Secret report helps Israelis to hide facts

Patrick Cockburn: Secret report helps Israel to hide facts

The slickness of Israel's spokesmen is rooted in directions set down by pollster Frank Luntz
The man who dared to go on holiday

The man who dared to go on holiday

New York's mayor has taken a vacation - in a nation that has still to enforce paid leave, it caused quite a stir, reports Rupert Cornwell
Best comedians: How the professionals go about their funny business, from Sarah Millican to Marcus Brigstocke

Best comedians: How the professionals go about their funny business

For all those wanting to know how stand-ups keep standing, here are some of the best moments
The Guest List 2014: Forget the Man Booker longlist, Literary Editor Katy Guest offers her alternative picks

The Guest List 2014

Forget the Man Booker longlist, Literary Editor Katy Guest offers her alternative picks
Jokes on Hollywood: 'With comedy film audiences shrinking, it’s time to move on'

Jokes on Hollywood

With comedy film audiences shrinking, it’s time to move on
It's the best of British art... but not all is on display

It's the best of British art... but not all is on display

Voted for by the British public, the artworks on Art Everywhere posters may be the only place where they can be seen
Critic claims 'I was the inspiration for Blanche DuBois'

Critic claims 'I was the inspiration for Blanche DuBois'

Blanche Marvin reveals how Tennessee Williams used her name and an off-the-cuff remark to create an iconic character
Sometimes it's hard to be a literary novelist

Sometimes it's hard to be a literary novelist

Websites offering your ebooks for nothing is only the latest disrespect the modern writer is subjected to, says DJ Taylor
Edinburgh Fringe 2014: The comedy highlights, from Bridget Christie to Jack Dee

Edinburgh Fringe 2014

The comedy highlights, from Bridget Christie to Jack Dee
Dame Jenny Abramsky: 'We have to rethink. If not, museums and parks will close'

Dame Jenny Abramsky: 'We have to rethink. If not, museums and parks will close'

The woman stepping down as chair of the Heritage Lottery Fund is worried