Two scientists who made landmark discoveries about human senses have won the Nobel Prize for Medicine, beating vaccine pioneers to the prestigious award.
The two Americans, David Julius and Lebanon-born Ardem Patapoutian, were named the winners on Monday after making breakthrough findings on how people sense heat, cold and touch.
Announcing the winners after balloting behind closed doors on Monday, the Nobel jury said the US duo had broken open a "fundamental unsolved question" about human biology.
"This really unlocks one of the secrets of nature," said Thomas Perlmann, the secretary of the Nobel Committee.
"It's actually something that is crucial for our survival, so it's a very important and profound discovery."
The winners were informed early on Monday. "They were incredibly happy, and as far as I could tell, they were very surprised," Mr Perlmann said. Nominees are not told that they are under consideration.
Mr Perlmann could not initially reach Dr Patapoutian in the early hours of the California morning. But Nobel organisers managed to track down the scientist's 92-year-old father, who passed on the message.
"I heard it from him, which was very special," said Dr Patapoutian.
The coveted award comes with a gold medal and 10 million Swedish krona ($1.14m), which is drawn from a bequest by Swedish industrialist Alfred Nobel in 1895.
Chili pepper breakthrough
Dr Julius, 65, is a professor at the University of California, San Francisco who used a pungent substance found in chili peppers to find a sensor in the skin that detects heat. His research stretches back to the 1990s.
He identified a single protein that makes people react to the chemical and to other painful sensations. His laboratory has used chemicals from horseradish and wasabi and toxins from snakes and tarantulas.
"David’s work epitomises the creativity, scientific rigour, and courage needed to pursue the major unsolved mysteries of biology," said university chancellor Sam Hawgood.
Dr Patapoutian, who was born in Lebanon in 1967 and moved to the US as a young man, works at Scripps Research in La Jolla, California. He identified genes that control sensitivity to touch.
The proteins he discovered also play a role in how people sense motion and how the body deals with blood pressure, respiration and bladder control.
He said his research had shone light on fundamental human behaviour which many people rarely question. "In science, many times, it’s the things that we take for granted that are of high interest," he said.
"Being in the field of sensing touch and pain, this was kind of the big elephant in the room... it was a difficult question to answer."
The findings made by the two scientists are being used to develop treatments for a range of ailments, including chronic pain, the Nobel jurors said.
Abdel El Manira, a member of the Nobel committee, said the receptors discovered by the two scientists helped people to avert danger.
"If we put our hand in a burning fire, these receptors send information to our brain and tell us to avoid touching a burning place," he said.
Nobel nominations are kept secret for 50 years, meaning there is no word on who else was considered for the prize.
Nobel season begins
Vaccine scientists won other prestigious awards this year, fuelling speculation that they would be in line for the Nobel after helping to turn the tide against Covid-19.
The fact they were overlooked this year does not mean they cannot win in the future. Scientists sometimes win a Nobel many years after their discovery.
The other Nobel Prizes, which honour outstanding work in the fields of physics, chemistry, literature and peace, will be handed out later this week.
A prize for economics, which was not one of the original awards created by Alfred Nobel, was added in 1968. The winner will be named next week.