Well, What if The Flintstones took place not in the past but, is in fact, the post apocalyptic future of The Jetsons? It is believed that a nuclear war occurred hundreds of years prior to The Flintstones, and that the characters from the Flintstones were all that remained of a war-torn world. It is also believed that after this catastrophic war, many people evacuated from the Earth, and built houses in the air. When the radioactive levels went down, several of these sky-ridden individuals returned to the ground to repopulate the Earth. Many animals were also presumably mutated into dinosaurs from the nuclear fallout of the war.