The back story.
This is something that used to concern space activists even in the seventies:
“In my comic, our civilization is long gone. Every civilization with written records has existed for less than 5,000 years; it seems optimistic to hope that the current one will last for 10,000 more,” Munroe told WIRED. “And as astronomer Fred Hoyle has pointed out, since we’ve stripped away the easily-accessed fossil fuels, whatever civilization comes along next won’t be able to jump-start an industrial revolution the way we did.”
You could think of fossil fuels as the yolk of an egg. If we eat it up, but fail to hatch and get into space, then this planet won’t reproduce.