In the 1992 comedy Encino Man, two California teenagers unearth a frozen caveman while digging a pool in their back yard. With the aid of some space heaters in the garage, he comes back to life, and fish-out-of-water hijinks ensue.
A human hibernation lasting several millennia is still pretty far-fetched, but the science behind shorter periods of therapeutic hypothermia is becoming ever more real.
Doctors at UPMC Presbyterian Hospital in Pittsburgh are beginning the first-ever human trials of "suspended animation" among gunshot victims with potentially fatal injuries. In order to buy more time to fix their wounds, doctors will replace all of the patients' blood with a saline solution, which will cool down the body and practically stop cellular activity.
As they're coursing with saline, the patients will be technically dead: They won't breathe, and there will be no brain activity. But the cells will stay alive, working at a much slower pace at the lower temperature. After about two hours, the doctors will re-infuse the patients with blood, and they should come back to life as though they had just taken a brief, frosty nap. The scientists who study this phenomenon have a common refrain: "You're not dead until you're warm and dead."