A group of 15 volunteers has left a cave in southwestern France where they had stayed for 40 days, in an study called the "Deep Time" project probing the limits of human adaptability to isolation, reports RFI.
Dazzled by the light and with pale faces but otherwise healthy, the group led by French-Swiss explorer Christian Clot emerged at around 10:30 am (0830 GMT) from the Lombrives cave in Ariège.
The underground isolation experiment saw the subjects, aged between 27 and 50, give up watches, phones and natural light, exchanging modern comforts for a cave system with a constant 12 Celsius (54 Fahrenheit) temperature and 95 percent humidity.
Members had to generate their own electricity with a pedal bike and draw water from a well 45 metres below the earth.
Clot, founder of the Human Adaptation Institute, had said the "Deep Time" experiment would test humans' ability to adapt to the loss of their frame of reference for time and space.