Fifteen people have emerged from a French cave after spending 40 days in voluntary isolation with no sense of time or date.
The eight men and seven women who took part in a scientific experiment emerged from their self-segregation in the Pyrenees on Saturday morning.
With big smiles on their pale faces, the 15 participants left the Lombrives cave to a round of applause and basked in the light of day while wearing special glasses to protect their eyes after so long in the dark.
For 40 days and 40 nights, the group lived in and explored the a dark, damp and vast cave without any sense of time.
There were no clocks and no sunlight inside, where the temperature was 10C (50F) and the relative humidity stood at 100%.
The cave dwellers had no contact with the outside world, no updates on the pandemic or any communication with friends and family above ground.
Scientists at the Human Adaptation Institute leading the 1.2 million-euro (£1 million) Deep Time project said the experiment will help them better understand how people adapt to drastic changes in living conditions and environments.
In partnership with labs in France and Switzerland, scientists monitored the 15-member group’s sleep patterns, social interactions and behavioural reactions via sensors.
One of the sensors was a tiny thermometer inside a capsule that participants swallowed like a pill to measure body temperature and transmit data to a portable computer until they expelled it naturally.
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.
“It’s really interesting to observe how this group synchronises themselves,” project director Christian Clot said in a recording done 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, two-thirds of them expressed a desire to remain underground for a little longer in order to finish group projects they had started during the expedition, Benoit Mauvieux, a chronobiologist involved in the research, added.