In the summer of 2023, a dozen people willingly walked into a steel chamber at the University of Ottawa designed to test the limits of human survival. Outfitted with heart rate monitors and temperature probes, they waited in temperatures of 42 degrees Celsius, or 107 degrees Fahrenheit, while the humidity steadily climbed, coating their bodies in sweat and condensation. After several hours, their internal body temperatures began ratcheting upward, as the heat cooked them from the outside in.
“Few people on the planet have actually experienced temperatures like this,” said Robert Meade, a postdoctoral researcher in epidemiology at the Harvard School of Public Health who led the study. “Imagine moisture condensing on the skin like a glass of water on a hot day. That’s how hot it was, compared to skin temperature.”
Their experiment tested the body’s ability to cope with extreme heat by exposing participants to temperatures at which they could no longer cool themselves. Their study confirmed that this dangerous threshold is much lower than scientists had previously thought: a so-called wet-bulb temperature, which accounts for heat and humidity, of 26 to 31 degrees C.
https://archive.ph/Lj16Y
As far as I can tell, this same research methodology would say that humans can't survive temperatures below 18 degrees Celsius. Put someone in a small room and tell them not to do anything useful to solve their problem, and they're going to do very poorly.
We are defined by our tool use, and not being able to survive the outdoors without wearing anything to suit the local environment is pretty common across the world.
Yeah, I hate when the temperature falls below 18 degrees Celsius! There have been times when I've gotten so uncomfortable that I've had to put some pants on. It's possible to survive it, for sure, but it sucks.