Teenage Cave Man

Teenage Caveman in the UK called Out of the Darkness is an independently made 1958 blackandwhite science fiction film produced and directed by Roger Corman, starring Robert Vaughn and Darah Marshall. The film was originally shot as Prehistoric World, but the title was changed by its distributor, American International Pictures, and then released on a double feature with How to Make a Monster 1958.

In a surprising denouement provided by the ancient man after his death, the truth is revealed in voiceover as the tribesman page through his book He was actually a survivor of a longago nuclear holocaust who was forced to live for decades inside his now ragged, discolored, and bulky radiation suit which is implied to have once been covered with deadly radioactive fallout. The ancient man has wandered the land for decades while the primitive remnants of a devastated human race have slowly increased their numbers, his frightening outer appearance causing them to fear and shun him.A final, cautionary question is asked in voiceover by the old man Will humanity someday repeat its nuclear folly after civilization has once again risen to its former heights? ........

Source: Wikipedia