The history
4,000 years from Bronze Age perfume workshops to the genes for 400 smell receptors, a gas that was given a smell to save lives, and a virus that took smell from millions.
People have made perfumes, burned incense and prized spices for thousands of years, but for most of history nobody knew how the nose actually smells. Philosophers guessed that smells were made of shaped particles, doctors tried to sort smells into classes, and scientists built machines to measure how faint a smell could be. Only in 1991 were the genes for smell receptors found, revealing a system of about 400 locks that read molecules like barcodes. Today smell is studied for safety, food, memory and medicine.
c. 1200 BCE
First chemist known by name, a perfumer
Tapputi, Babylonian Mesopotamia
1888
First instrument to measure smell strength
Hendrik Zwaardemaker, Netherlands
1937
First law requiring gas to be given a smell
Texas, USA
1982
First electronic nose
Persaud and Dodd, University of Warwick, UK
1991
Smell receptor genes discovered
Linda Buck and Richard Axel, USA
2004
Nobel Prize for the sense of smell
Linda Buck and Richard Axel
2000 BCE – 1650
Perfumers in Cyprus, Egypt, Mesopotamia, Persia and India master scents, while thinkers guess that smells are made of shaped particles.
2000 BCE
c. 2000 BCE
Archaeologists digging at Pyrgos on Cyprus found a large workshop, dated to about 4,000 years ago, with stills, jugs and bowls for making scented oils. From residues in the pots they recreated perfumes of pine, coriander, bay and rosemary.
Why it mattered. It shows that making smells on purpose is one of the oldest crafts people have.
1470 BCE
c. 1470 BCE
Carvings at Hatshepsut’s temple at Deir el-Bahari show her ships returning from the land of Punt with myrrh, incense and living incense trees in baskets. Temples burned incense every day, and Egyptians used scented oils for the living and the dead.
Why it mattered. Ancient Egypt treated fragrance as precious and sacred, worth sending a fleet for.
1200 BCE
c. 1200 BCE
A cuneiform clay tablet from Babylonian Mesopotamia names Tapputi, a woman who oversaw perfume-making at the royal palace. It describes her mixing flowers, oil and calamus with water or other solvents, then distilling and filtering them.
Why it mattered. She is often called the first chemist whose name we know, and she was a perfumer.
300 BCE
c. 300 BCE
Theophrastus, a student of Aristotle, wrote a short work, On Odours, about scents, perfumes and how they are made and kept. He noted that smells are hard to name and classify, a problem scientists still wrestle with.
Why it mattered. It is one of the earliest attempts to write down what smells are and how they work.
55 BCE
1st century BCE
In his long poem On the Nature of Things, the Roman poet Lucretius explained smells, like tastes, with tiny atoms. Pleasant smells, he wrote, come from smooth, round atoms, and harsh ones from rough, hooked atoms that scrape the nose.
Why it mattered. The idea that a smell depends on the shape of its particles comes back, in a new form, 2,000 years later.
850
9th century (attributed)
The Arab scholar al-Kindi is credited with a Book of the Chemistry of Perfume and Distillations, with over a hundred recipes for scented oils, salves and waters, and the methods to make them.
Why it mattered. It records perfume-making as careful chemistry, with written recipes others could repeat.
1020
early 11th century (attributed)
Ibn Sina is often credited with improving steam distillation to capture the essential oil of roses, though rose water was being distilled before him. Rose water and rose oil became famous trade goods across the Islamic world and beyond.
Why it mattered. Distillation let perfumers capture a flower’s smell molecules in a bottle.
1600
by the 1600s (a centuries-old tradition)
In Kannauj, families have distilled flowers, herbs and even baked earth into attar for more than 400 years. They use the deg-bhapka method: copper stills over wood fires, with the scented steam caught in sandalwood oil. In 2014 Kannauj Perfume received a Geographical Indication tag.
Why it mattered. It is one of the world’s oldest living perfume traditions, still made by hand today.
1650 – 1885
Naturalists try to classify smells like plants and animals, and anatomists wrongly decide that humans are poor smellers.
1752
In a medical dissertation on the odours of medicines, Linnaeus sorted smells into seven classes: aromatic, fragrant, ambrosial (musky), alliaceous (garlicky), hircine (goaty), repulsive and nauseating.
Why it mattered. It was an early attempt to organise smells like plants, and it showed how hard smells are to classify.
1879
The anatomist Paul Broca noticed that the human olfactory bulb is small compared with the rest of our brain and grouped humans with the “non-smellers”. He did no smell tests. The idea that humans have a poor sense of smell stuck for over a century.
Why it mattered. Modern tests show human noses are far better than this old myth suggests.
1885 – 1970
Scientists measure smell strength, writers notice smell’s link to memory, a disaster gives gas a smell, and the lock-and-key idea is born.
1888
Zwaardemaker built a device with a glass tube that slid inside a tube lined with a smelly material. Sniffing through it, a person got a stronger smell the further the tube was pulled out, so the weakest detectable smell could be measured.
Why it mattered. For the first time, the strength of a smell and a person’s sensitivity could be put into numbers.
1913
In the novel Swann’s Way, the narrator dips a small cake, a madeleine, into tea. Its taste and smell bring back a flood of childhood memories he had forgotten. Scientists now call smell-triggered memories the “Proust effect”.
Why it mattered. It gave a name to something everyone has felt: smells unlock memories.
1937
18 March 1937
Unsmelled natural gas leaked and built up under a school, and a spark set it off. Around 300 people, most of them children, were killed. Texas then passed a law requiring gas to carry a strong smell, a “malodorant”, and other places followed. Today mercaptans such as ethyl mercaptan, added to LPG, do this job.
Why it mattered. The smell of a gas leak is a safety feature, added so that noses can raise the alarm.
1964
1952–1964
Amoore proposed that smell depends on molecules fitting receptor sites of certain shapes, like keys in locks, and suggested seven primary odours. He set it out for the public in Scientific American in 1964. Later he agreed there must be many more than seven kinds of receptor.
Why it mattered. He was right that shape matters, even though the real system turned out to be far bigger.
1965 – 2012
Mirror-image molecules, electronic noses and the discovery of the receptor genes reveal how the nose really reads molecules.
1971
Two teams showed that the two mirror-image forms of carvone smell different: one of spearmint, the other of caraway. The molecules have exactly the same atoms, arranged as left and right hands.
Why it mattered. It proved that the nose reads a molecule’s 3D shape, not just what it is made of.
1982
Persaud and Dodd built a “model nose” from a few chemical sensors that each responded broadly to many smells. By comparing the pattern across sensors, it could tell different odours apart.
Why it mattered. It showed that a pattern from broadly tuned sensors is enough to tell smells apart, the same trick the real nose uses.
1991
5 April 1991
Buck and Axel discovered a huge family of genes for odorant receptors, proteins on the cilia of smell neurons. In mice there are about 1,000; humans have about 400 that work. They showed each neuron uses just one receptor type.
Why it mattered. It explained, at last, how the nose can detect so many different molecules.
2004
4 October 2004
Buck and Axel were awarded the Nobel Prize in Physiology or Medicine “for their discoveries of odorant receptors and the organization of the olfactory system”, including how neurons of one type all wire to the same spots in the olfactory bulb.
Why it mattered. Smell, long the least understood sense, joined the best understood.
2008
Studying human olfactory bulbs, researchers found more than 5,500 glomeruli on average, about 16 for each receptor type, not the 2 per type seen in mice.
Why it mattered. Human smell wiring turned out to differ from the mouse model everyone had assumed.
2012 – today
Debates about how many smells we can tell apart, super-smellers, and COVID-19 put the sense of smell in the news.
2014
21 March 2014
Volunteers compared mixtures of many odour molecules and tried to spot the odd one out. From the results the team estimated that people can tell apart at least a trillion different smells, and the number made headlines.
Why it mattered. It overturned the old, never-tested claim that humans can tell apart only about 10,000 smells.
2015
Two papers showed that the trillion figure depended heavily on the maths used. With the same method, the answer could be far bigger or far smaller, and applied to colour vision it gave nonsense. The true number of smells we can tell apart is still unknown.
Why it mattered. Big numbers need careful checking: the question is still open.
2017
A review in Science traced the idea that humans are poor smellers back to Broca, and showed that in tests people can match or beat dogs and rodents at detecting some smells.
Why it mattered. It helped end a 140-year-old myth about the human nose.
2019
March 2019
Joy Milne, a retired nurse, noticed a musky smell on her husband years before he was diagnosed with Parkinson’s disease. Scientists used her nose to find molecules in skin oil (sebum) that differ in people with Parkinson’s.
Why it mattered. One unusual nose pointed chemists towards a possible simple test for a disease.
2020
March to May 2020
In March 2020, ear, nose and throat doctors warned that sudden loss of smell could be a sign of COVID-19. On 18 May 2020 the UK added it to the official symptom list. Early studies found smell loss in roughly 40 to 50% of patients, far fewer with the later Omicron variant.
Why it mattered. Millions of people discovered how much they rely on a sense they had never thought about.
2020
24 July 2020
Researchers found that the proteins the virus uses to enter cells are made by the supporting cells of the smell patch, not by the smell neurons themselves. Damage to these helper cells disrupts smell.
Why it mattered. It explained why most people recover: the neurons are mostly spared and the support cells regrow.
2021
4 October 2021
David Julius shared the Nobel Prize for discovering TRPV1, the sensor that capsaicin in chilli triggers, and, with others, the menthol sensor TRPM8. These sit on the trigeminal nerve endings in the mouth and nose.
Why it mattered. It explains why chilli burns and mint cools, even though neither is a taste or a smell.
Did you know?
The smell patch in each side of your nose is only about the size of a postage stamp.
Humans have about 400 working smell receptor genes; mice have about 1,100.
Spearmint and caraway get their smells from two mirror-image forms of the same molecule, carvone.
Cooking gas has almost no smell of its own. The smell is added so noses can spot a leak at around one part per billion.
Early in the COVID-19 pandemic, roughly 40 to 50% of patients lost some sense of smell.
The people
fl. c. 1200 BCE · Perfumer and palace overseer · Babylonian Mesopotamia
The first chemist known by name, recorded making perfumes by distilling and filtering.
c. 99 – c. 55 BCE · Poet and philosopher · Rome
Explained smells as atoms of different shapes, smooth or hooked.
1707 – 1778 · Naturalist and physician · Sweden
Sorted smells into seven classes in 1752.
1857 – 1930 · Physiologist · Netherlands
Invented the olfactometer to measure how faint a smell can be.
20th century · Biochemist · United Kingdom
Championed the idea that molecules fit smell receptors by shape.
born 1947 · Neuroscientist · United States
Co-discovered the smell receptor genes and shared the 2004 Nobel Prize.
born 1946 · Molecular biologist · United States
Co-discovered the smell receptor genes and shared the 2004 Nobel Prize.
20th–21st century · Retired nurse · Scotland, UK
Could smell Parkinson’s disease, which led chemists to new biomarkers.
Where it happened
Sources
Dates marked “c.” are approximate, and historians sometimes disagree about who was first. If you spot a mistake, tell us.
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