RFTG:
Mine started off as a childs story, naive and full of spelling errors. "I Live In A Big City" by Will Price, age 7. He describes his lifestyle and stuff, and then talks how he learnt at school about the people in the tribes out in the desert... and how unlucky they are to not have electricity or heating or medicine.
That part ends and it switches to third person narrative...
Cut forward a few hundred years, a young child from a tribe finds the story on fading paper in a crumbling building. He shows it to the village elder, who tells him of the city people long ago and how were all killed by smog inhalation because of the pollution, caused by their machines, and how it's now ironic that the only survivors (the tribal people who lived far enough away to not be poisoned by smog) have to hide in the ruined cities to escape acid rain etc. The boy is full of wonder over things like supermarkets (where you can get already-dead animals so you don't have to hunt them!) and heaters (his mother died in the last winter). But the elder says that these things contributed to the pollution while simultaneously helping the city-folk.
Cut back to the present, to little Will showing his father the story he wrote about his life in the city, and his father telling Will he should be proud that he belongs to civilisation, and his descendants will survive when the tribes are dying from disease and famine. I had the father say the Mark Twain quote somewhere in there, explaining that they were lucky to be part of the majority who had electricity. End with Will's father turning up the heater.
... I probably should have made the demise of civilisation a little more realistic than "they all choked to death" =P ... could've said something about acid rain and smog killing crops and therefore livestock died and therefore people died from lack of food... And I think I polarized too much. Ah well. ^ ^ ... Yeah, and it was crap. I think the space of a few hundred years for all civilisation to be dead and crumbling, is also unrealistic. Go me! ^ ^;