'Deep Time' project: French cave isolation study ends after 40 days

Members of the French team emerge from the Lombrives Cave after 40 days underground in Ussat les Bains, France. Photo / AP

Ever wonder what it would feel like to unplug from a hyperconnected world and hide away in a dark cave for 40 days?

Fifteen people in France did just that, emerging on Saturday (local time) from a scientific experiment to say that time seemed to pass more slowly in their cavernous underground abode in southwestern France, where they were deprived of clocks and light.

With big smiles on their pale faces, the 15 left their voluntary isolation in the Lombrives cave to a round of applause and basked in the light while wearing special glasses to protect their eyes after so long in the dark.

Members of the team taking part in the 'Deep Time' study eat, in the Lombrives Cave in Ussat les Bains, France. Photo / via AP

"It was like pressing pause," said 33-year-old Marina Lançon, one of the seven female members in the experiment, adding she didn't feel there was a rush to do anything.

Although she wished she could have stayed in the cave a few days longer, she said she was happy to feel the wind blowing on her face again and hear the birds sing in the trees of the French Pyrenees. And she doesn't plan to open her smartphone for a few more days, hoping to avoid a "too brutal" return to real life.

For 40 days and 40 nights, the group lived in and explored the cave as part of the Deep Time project. There was no sunlight inside, the temperature was 10C and the relative humidity stood at 100 per cent. The cave dwellers had no contact with the outside world, no updates on the pandemic nor any communications with friends or family.

Scientists at the Human Adaption Institute leading the €1.2 million ($1.5m) "Deep Time" project say the experiment will help them better understand how people adapt to drastic changes in living conditions and environments.

As expected, those in the cave lost their sense of time.

Eight men and seven women lived in the Lombrives cave in the Pyrenees to help researchers understand how people adapt to drastic changes in living conditions and environments. Photo / via AP

"And here we are! We just left after 40 days ... For us it was a real surprise," said project director Christian Clot, adding for most participants, "in our heads, we had walked into the cave 30 days ago."

At least one team member estimated the time underground at 23 days.

Johan Francois, 37, a maths teacher and sailing instructor, ran 10km circles in the cave to stay fit. He sometimes had "visceral urges" to leave.

With no daily obligations and no children around, the challenge was "to profit from the present moment without ever thinking about what will happen in one hour, in two hours," he said.

In partnership with labs in France and Switzerland, scientists monitored the 15 member's sleep patterns, social interactions and behavioral reactions via sensors. One sensor was a tiny thermometer inside a capsule that participants swallowed like a pill. It measured body temperatures and transmitted data to a computer until it was expelled naturally.

French team members celebrate as they emerge from the Lombrives Cave after 40 days underground in Ussat les Bains, France. Photo / AP

The team members followed their biological clocks to know when to wake up, go to sleep and eat. They counted their days not in hours but in sleep cycles.

Scientists monitoring the participants entered the cave to let the research subjects know they would be coming out soon.

"It's really interesting to observe how this group synchronises themselves," Clot said earlier in a recording from inside the cave. Working together on projects and organising tasks without being able to set a time to meet was especially challenging, he said.

Although the participants looked visibly tired on Saturday, two-thirds expressed a desire to remain underground a bit longer in order to finish group projects started during the expedition, Benoit Mauvieux, a chronobiologist involved in the research, told the AP.

"Our future as humans on this planet will evolve," Clot said after emerging. "We must learn to better understand how our brains are capable of finding new solutions, whatever the situation."

- AP