Toba

You are one of perhaps a thousand people left alive on Earth. Not a thousand in your village — a thousand in the world. Behind you, to the south, a mountain has just torn itself apart so completely that the sky has turned the colour of a bruise and stayed that way for years. The sun still rises, technically. But it brings no warmth. The crops that don't exist yet would have failed. The animals are gone or dying. You don't know any of this in words. You know it in hunger, and cold, and the terrible quiet where birdsong used to be.

This really happened. A supervolcano called Toba erupted with a force that dwarfs anything in recorded human history, and what followed — decades of volcanic winter, collapsed ecosystems, a planet suddenly hostile to the primate that thought it was flourishing — nearly finished us before we started. Geneticists can read the scar in your DNA right now. Every person alive today descended from so few survivors that we are, by the standards of other species, suspiciously identical. A cheetah has more genetic variety than eight billion humans.

The people who held on — and we don't know how, or exactly where, or how many — were not special. They were the ones who didn't die. And everything you are came from them.