The Time We Almost Ended

There is a disaster written into your genes. For a species spread across an entire planet, humans are eerily alike — far less genetically varied than a single troop of chimpanzees in one forest. The most natural explanation is grim: at some point our ancestors crashed to a tiny number, squeezed through a narrow gate that very nearly closed for good.

By some estimates the whole of humanity fell to a few thousand individuals — perhaps fewer — clinging on somewhere, for generations, on the edge of vanishing. We are not certain what did it; a brutal swing of climate, possibly a distant supervolcano darkening the sky. Whatever it was, every person now alive is descended from the handful who came through it.

Eight billion of us, and the entire line runs back through a group that could have huddled in one village — a group that, for a while, very nearly didn't make it at all.

And if we slipped through one gate already — were there other humans who didn't?