Some ideas for a novel

The plot would be as follows:

In the future, Earth's most intelligent has abandoned the planet. They created a massive starship/planetship that would be able to house and sustain the chosen people in their journey towards a new home.

Meanwhile in Earth:

Only a few intelligent people has chosen to remain in the planet. Some are deliberately left there. The non-intelligent humans are left to fend for themselves. Technology crumbles and they slowly lost the ability to manufacture and study the technology. They continue to produce offspring and, further generations down, these people marvel at the technological advance of the Chosen Smart, thinking it was the work of a supernatural or extraterrestrial entity.

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