Many would probably survive, and would have to live through a long gradual decline into anarchy and barbarism. Imagine how fucking useless contemporary people would be in a post apocalyptic society. A comet or a solar flare could send us back to the bronze age overnight, and pretty much all of our scientific advances would be forgotten in a generation or two.
I think a civ can be a lot more advanced than we are and still get utterly erased by nature.
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