Not the extreme temperature that the OP is talking about but in the early days of the space race NASA tested for many extreme conditions. I remember reading about a test where a person was in a large oven at around 350 degrees F. The subject had a loose fitting aluminum foil face shield to avoid harming the eyes and mouth but other then that he sat there for about a half hour as I recall.
How does an oven bake meat, cake, pie at 350 F but not bake a human?
Humans are a lot bigger than a typical ham, and yet it still takes hours to cook the latter. It comes down to surface area: heat can only enter at the surface, so it can take a long time for heat to get to the center. Roasting a whole pig can take tens of hours; a human wouldn’t be that different.
Living humans also have temperature regulation. We can sweat, which takes heat away, and we have circulation that moves heat from hot spots to cooler spots. Air is not a very good conductor compared to water, so the body can keep the surface cool relatively easily.
As long as it’s a dry heat. 
But that’s not really a joke. If there were any significant levels of humidity, they would not have survived.
There were a number of human endurance tests and some of us tried to match a few. The one that seemed to be most obtainable was the hand immersed in hot water. The highest any of us got was about 115 degrees F as I recall. The hot oven test seems extreme but sweat does the trick. I wish I had a cite for the claims but I have tried a few times and never came up with the article. So it might have been 325 or whatever instead of 350 or 20 minutes instead of 30. But whatever it was it was impressive.
Tangents:
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Back when people were braver or more stupid, they used to demonstrate the Leidenfrost effect by using their hand and molten lead.
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There are national and international standards for how hot consumer and industrial equipment can be. One of the differences is that consumer equipment that people can touch, has to be safe for children and old people. “Safe” means that, when you touch it, you can feel the heat and move your self away from it fast enough to not get a burn. It’s different for children and old people, because they have thinner skin than adult male industrial workers, and burn at lower temperatures.
These standards are most important for metal objects: because of the poor heat transfer, wood and plastic tend to only get hot on the outside if heated from the outside.
Also like your skin, wood and plastic tend to degrade at temperatures hot enough to burn your skin, which is a reason not to use wood and plastic for hot objects.
Wood and plastic don’t transfer enough energy to do damage unless they are significantly hotter, but because of the poor heat transfer, wood and plastic surfaces can get significantly hotter from a smaller heat source, so it’s a different kind of problem, but still a problem.
Though a thing to keep in mind there is silicon based plastics. They do not degrade like regular plastic would when exposed to high temperatures (meaning oven temps, not millions of degrees as in the OP), and do have excellent heat retention and transfer capabilities.
I use 'em all the time for baking things, they are also a great non-stick surface. However, I have had people touch them right out of the oven and give themselves a bit of a burn.
Also, I think I remember them demonstrating that you could touch the space-shuttle insulation tiles when they were white-hot? Because they insulated so well, you didn’t get enough energy out of them to burn?
I think it meant putting your hand on the other side of the tiles, not actually the hot side itself.
A nice demo of the type of ceramic used, guy handles the cube of material after a few moments out of the high temperature oven:
From the one recording:
Recorded this video during my KSC tour 1 day before the launch of the Atlantis Space Shuttle for STS-135, the last Space Shuttle mission.
