Michel Siffre, ‘caveman’ who spent weeks underground

In 1962 Michel Siffre, a young French geologist, was planning a two-month research expedition to map a large underground glacier in the Alps. He had heard about Nathaniel Kleitman’s 1930s work on the human body clock and, almost as an afterthought, decided to descend into the dark cave with no way of keeping track of time or date. “I decided to live like an animal, without a watch, in the dark, without knowing the time,” he explained many years later, adding that doing so was “the great idea of my life”.
He denied himself valuable medical supplies while the only light was the skimpy ray from his four-volt lamp. He did, however, have some home comforts: a stove, a folding table and a gramophone, on which he played Beethoven’s Piano Concerto No 3. “I have an unforgettable, grandiose and almost tragic sensation in listening to this music resounding strangely in this cavern,” he recorded on day two of his diary, which was published as Beyond Time (1965) and serialised in The Observer.
A slightly built caveman at 5ft 4in, Siffre allowed his body clock to run free. He telephoned his support team before settling down to sleep and just after waking up, but they “didn’t have the right to call me, so that I wouldn’t have any idea what time it was on the outside”. In the gloom of the cave his body’s cycle extended to 24 hours and 30 minutes. His later experiments found that some people became more like hibernating animals, their days distorted to 48 hours.
The mission had begun as a geological one, involving the study of water flows, drawing maps of watercourses and tracing the shape of the ice crystals. “Later, while I am writing, a kind of ice block crashes down with a great din,” he observed on day five. Another fall on day seven precipitated his first panic attack. “I am very young to become a shapeless corpse, caught between two rocks,” he wrote.
Gradually day and night blurred into one. “I don’t know if I am nearer the 15th or 30th August,” he wrote, possibly on August 18. When his surface team telephoned to say that the experiment was over, he thought it was August 20; it was in fact almost four weeks later.
After about 1,500 hours in darkness, the prospect of daylight was overwhelming. Claude Sauvageot, a reporter from Le Figaro, was among those who entered the cave to escort him out. He encountered an unshaven figure who “looked terrifying and clambered from rock to rock as if he knew by heart the smallest foothold”. Everywhere lay half-empty tins of food, piles of debris and discarded torch batteries.
When he finally emerged, Siffre was unaware of the excitement he had generated. More than 100 people had gathered: police officers, journalists, TV crews, government officials and fellow geologists and speleologists. “Two doctors examined him, then a helicopter carried him to Nice, where his parents were waiting,” Sauvageot added. “He had won.”
Michel Siffre was born in 1939 in Nice and by the age of 13 was potholing and exploring underground caves. He studied geology, completing his education at the Sorbonne in Paris. In 1960 he received a grant for a caving expedition in Ceylon (now Sri Lanka).
The following year he discovered the underground Alpine glacier, about 70km (45 miles) from Nice. “At first, my idea was to prepare a geological expedition, and to spend about 15 days underground studying the glacier, but a couple of months later, I said to myself, ‘Well, 15 days is not enough. I shall see nothing.’ So, I decided to stay two months,” he told Cabinet magazine.
He repeated the experiment in 1972, spending 205 days in the aptly named Midnight Cave in Texas. “He must be mad. But there’s no means of stopping him,” his mother, Lucie, declared as he descended. This time he had backing from the French ministry of defence, keen to know how submariners might fare during lengthy missions underwater, and Nasa, which wanted to apply his findings to astronauts on lengthy space missions and civilians in nuclear fallout shelters.
The previous year he had married Nathalie, who was 13 years his junior. The marriage was soon dissolved. Siffre was now $100,000 in debt, partly because he had underestimated the costs of bringing his experiments from France to Texas and partly because the anticipated media coverage never materialised.
Both between and after his underground adventures Siffre was the chief researcher on several “out of time” trials. “I put a man in a cave for four months, then a woman for three months,” he said. “We analysed sleep stages … [and] showed that there is a correlation between how long a person stays up and how much he dreams the next night.”
Inspired by the American astronaut John Glenn’s return to space in 1998 at age 77, Siffre began a third and final prolonged underground stay in 1999. He was covered in electrodes to measure his heartbeat, breathing, temperature and sleeping patterns. This time he adjusted to a 48-hour cycle, eventually emerging from his cave at Clamouse in southern France on January 4, 2000, after more than two months, thinking he still had another week of solitude remaining.
Michel Siffre, underground explorer, was born on January 3, 1939. He died on August 25, 2024, aged 85