The history
From Aristotle and the six rasas of Ayurveda to a myth-making tongue map, the discovery of umami, and receptors for every taste.
People have argued about how many tastes there are for over 2,000 years. For most of that time taste was a matter of philosophy and cooking. Microscopes found the taste buds, careful tests found (and a misreading invented) a tongue map, and a Japanese chemist found a taste Europe had missed. In the last 30 years, genetics revealed the receptor for each of the five tastes, and showed that chilli heat is really a pain and heat sensor at work.
c. 350 BCE
Written list of basic tastes
Aristotle, Greece
c. 2nd century BCE to 2nd century CE
Six tastes as the basis of a healthy diet
Charaka Samhita, India
1867
Taste buds seen under the microscope
Christian Lovén and Gustav Schwalbe
1908
Umami identified
Kikunae Ikeda, Japan
1912
Chilli heat scale
Wilbur Scoville, USA
1997
Heat and capsaicin sensor (TRPV1) found
David Julius, USA
2007
Chilli certified above one million SHU
Bhut jolokia, north-east India
2018–2019
Sour receptor (OTOP1) identified
Liman and Zuker labs, USA
400 BCE – 1800
Philosophers and physicians in Greece and India sort tastes into short lists, including some, like pungent and astringent, that science now calls touch.
350 BCE
c. 350 BCE
In his book On the Soul, Aristotle wrote that the two basic tastes are sweet and bitter. Between them he placed oily, salty, pungent, harsh (astringent) and sour, a list of seven or eight flavours.
Why it mattered. It was one of the first attempts to sort tastes into a short list of basics, an idea still used today.
100 BCE
c. 2nd century BCE to 2nd century CE
The Charaka Samhita, a founding text of Ayurveda, describes six rasas, or tastes: madhura (sweet), amla (sour), lavana (salty), katu (pungent), tikta (bitter) and kashaya (astringent). A healthy diet, it says, balances all six. Its date is uncertain; it was revised over several centuries.
Why it mattered. Its six tastes include pungent and astringent, which science now files under touch and pain rather than taste, as this box shows.
1860 – 1975
Microscopes reveal the taste buds; a study of the tongue edge is misread into the famous tongue map, then tested and found wrong.
1867
Working separately, the Swedish anatomist Christian Lovén and the German anatomist Gustav Schwalbe looked at the tongue under the microscope and found small onion-shaped clusters of cells, which they called taste bulbs or taste goblets.
Why it mattered. It showed that taste is sensed by special groups of cells, not by the whole tongue surface.
1901
In a paper called "On the psychophysics of the sense of taste", Hänig dripped sweet, sour, salty and bitter solutions on spots around the edge of people's tongues and found the weakest strength each could notice. The differences between spots were small.
Why it mattered. His careful data were later misread as a tongue map, one of the most famous myths in science teaching.
1942
In his history of the psychology of the senses, Boring redrew Hänig's 1901 results as a graph of how sensitive each part of the tongue edge was, with no numbers on the scale. Readers took the peaks to mean each taste lived in only one area, and a tongue map spread into textbooks.
Why it mattered. It shows how a small misreading can travel for decades.
1965
By labelling new cells in rats, Beidler and Smallman showed that taste-bud cells are constantly replaced, living about ten days on average before new ones take their place.
Why it mattered. It explains why taste usually recovers after a burn from hot food or drink.
1974
Collings repeated the tests on many spots of the tongue and found that all four tastes then known could be sensed everywhere with taste buds. The weakest noticeable strength differed a little from place to place, but no area was blind to any taste.
Why it mattered. It was the scientific end of the tongue map, even if school books kept it for years.
1900 – 1995
A fifth taste is found in seaweed broth, chilli heat gets a scale, and some people turn out to be blind to a bitter chemical.
1908
The chemist Kikunae Ikeda wondered why kombu seaweed broth (dashi) tasted so savoury. He boiled down large amounts of kombu and extracted glutamic acid, whose salts gave the taste. He named it umami, from the Japanese for "delicious".
Why it mattered. It was the first scientific claim for a fifth basic taste, though the West took most of a century to accept it.
1909
Ikeda patented a way to make monosodium glutamate (MSG) and teamed up with the businessman Saburosuke Suzuki to sell it as a seasoning called Ajinomoto, "essence of taste".
Why it mattered. It turned a taste discovery into one of the world's most widely used food ingredients.
1912
The pharmacist Wilbur Scoville, working for the drug company Parke-Davis, soaked dried chillies in alcohol, then diluted the extract with sugar water until a panel of tasters could no longer feel the heat. The number of dilutions became the Scoville heat unit.
Why it mattered. It gave the world a scale for chilli heat, still used today, though labs now measure capsaicin with machines.
1931
Fox was pouring a powder called PTC when some of it blew into the air. His colleague C. R. Noller complained it was very bitter; Fox, standing closer, tasted nothing. Testing others showed that people differ: roughly a third of people worldwide cannot taste it.
Why it mattered. It was the first clear sign that taste is partly in our genes. The gene, TAS2R38, a bitter receptor, was found in 2003.
1985
Researchers from many countries met in Hawaii for the first international meeting on umami. Shizuko Yamaguchi showed with careful taste tests that umami could not be made by mixing the other four tastes, and "umami" was adopted as the scientific name for the taste of glutamate.
Why it mattered. It put umami on the world's scientific map, though its receptor was still unknown.
1994
Bartoshuk's team found that people fall into three groups for the bitter chemical PROP: non-tasters, medium tasters and "supertasters", who find it intensely bitter and tend to have more fungiform papillae. In their samples, about a quarter of people were supertasters.
Why it mattered. It showed that people really do live in different taste worlds.
1997 – 2019
Genetics finds the sensors: T1Rs for sweet and umami, T2Rs for bitter, ENaC for salt, OTOP1 for sour, and TRP channels for heat and cold.
1997
Julius's team searched through thousands of genes for one that made cells respond to capsaicin. They found TRPV1, a channel that also opens at painful heat above about 43 °C.
Why it mattered. It explained why chilli feels hot, and opened the science of how we sense temperature.
2000
Three papers described the T2Rs, a family of about 25 bitter receptors in humans. Many bitter cells carry several kinds, so one cell can warn of many different poisons. The same year, a team in Miami proposed a glutamate receptor for umami.
Why it mattered. It showed why bitter is so sensitive: it is a warning system built to catch thousands of chemicals.
2001
2001–2002
Teams found a third gene, T1R3, and showed that T1R2 + T1R3 together make the sweet receptor (2001), while T1R1 + T1R3 make the umami receptor for glutamate (2002).
Why it mattered. Umami finally had a receptor of its own, and its place as the fifth basic taste was settled.
2002
Two teams independently found TRPM8, a channel on nerve endings that opens with cool temperatures and with menthol from mint.
Why it mattered. It explained why mint feels cold even when it is not.
2010
Mice without the sodium channel ENaC in their taste cells lost their liking for low salt. So ENaC is the sensor for pleasant saltiness, while very salty food also triggers bitter and sour cells.
Why it mattered. It explained why a little salt tastes good and a lot tastes bad.
2015
Taste tests suggested that fatty acids have a taste of their own, which the team proposed calling "oleogustus". Earlier work had found fat-sensing receptors such as CD36 on taste cells. Scientists still debate it, along with "kokumi", a richness linked to a calcium-sensing receptor.
Why it mattered. The list of basic tastes may not be finished.
2018
2018–2019
Sour was the last basic taste without a known receptor. In 2018 Liman's team showed that OTOP1, a channel that lets protons in, is found in sour cells. In 2019 her lab and Zuker's showed that mice without it barely sense sour.
Why it mattered. It completed the set: each of the five tastes now has a known sensor.
2007 – today
Chilli breeders chase heat records, COVID-19 shows the world how flavour depends on smell, and the heat sensor wins a Nobel Prize.
2007
February 2007
Guinness World Records certified the bhut jolokia, the "ghost pepper" grown in Assam and nearby states, as the world's hottest chilli, after lab tests measured 1,001,304 Scoville heat units.
Why it mattered. It was the first chilli certified above a million SHU, nearly double the previous record holder.
2013
November 2013
Guinness World Records confirmed the Carolina Reaper, a cross-bred chilli, as the hottest, at an average of 1,569,300 Scoville heat units; a 2017 re-test put it at 1,641,183.
Why it mattered. Breeders were now deliberately crossing chillies to push the heat higher.
2020
During the COVID-19 pandemic, sudden loss of smell, and with it much of the sense of taste, became one of the best-known symptoms. Health services such as the UK's NHS and the US CDC added it to their symptom lists in 2020.
Why it mattered. Millions of people learned how much of flavour depends on smell, and research into smell loss grew fast.
2021
October 2021
The Nobel Prize in Physiology or Medicine went to Julius, for finding TRPV1 with capsaicin, and to Patapoutian, for finding the touch sensors PIEZO1 and PIEZO2. Both also found TRPM8, the cold sensor.
Why it mattered. The science behind chilli heat and minty cool reached the top of medicine.
By the numbers
Guinness-certified record holders: from the first million-SHU chilli in 2007, breeders have pushed the heat up by about two and a half times.
Did you know?
The tongue map, with sweet on the tip and bitter at the back, is a myth: every part with taste buds tastes all five.
You can notice bitter quinine at a strength over 1,000 times weaker than the weakest sugar you can notice.
Chilli heat is not a taste: capsaicin opens TRPV1, the same sensor that warns of burning heat above about 43 °C.
Your taste cells are replaced about every ten days, some after a few weeks.
Ayurveda counted six tastes about 2,000 years ago; two of them, pungent and astringent, are now known to be touch and pain rather than taste.
The people
384 – 322 BCE · Philosopher · Greece
Made one of the first lists of basic tastes, with sweet and bitter as the extremes.
1864 – 1936 · Chemist · Japan
Found glutamate in kombu broth and named its taste umami.
1865 – 1942 · Pharmacist · USA
Invented the dilution test that still gives chilli heat its units.
active 1930s · Chemist · USA
Discovered by accident that some people cannot taste the bitter chemical PTC.
20th century · Psychologist · USA
Tested the tongue map in 1974 and showed that every area with taste buds senses every taste.
born 1938 · Taste scientist · USA
Found supertasters and showed how differently people experience taste.
Zuker born 1957 · Neuroscientists · Chile and the UK, working in the USA
Their labs found or pinned down receptors for sweet, umami, bitter, salt and sour.
20th–21st century · Neuroscientist · USA
Her lab identified OTOP1, the proton channel behind sour taste.
born 1955 · Physiologist · USA
Used capsaicin to find TRPV1, the heat sensor; Nobel Prize 2021.
born 1967 · Neuroscientist · Lebanon, working in the USA
Found the touch sensors PIEZO1 and PIEZO2 and co-discovered the cold sensor TRPM8; Nobel Prize 2021.
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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