The Loneliest Breeding Pool on Earth

Every stranger you pass is your distant cousin — and here is why that sentence is not a metaphor. At some point in the past, the entire human species fit inside a single stadium. Not a city. Not a village network. A stadium. Geneticists read this in your blood: the variation between any two humans alive today is astonishingly small — smaller than the variation inside a single troop of chimpanzees. We are, genetically speaking, almost identical. And that sameness has a cause, one that was almost a death sentence.

Somewhere around 70,000 years ago, something nearly finished us. A volcano, most likely — Toba, in what is now Indonesia, which erupted with a force that dimmed the sun for years and dropped temperatures across the planet. The best current estimate is that the human population collapsed to somewhere between 1,000 and 10,000 people. Perhaps fewer. A handful of groups, frightened and hungry, clinging to coastlines in Africa while the world went cold around them.

Every person alive today descends from those survivors. Your DNA is their DNA, shuffled and re-dealt across 70,000 years. The stranger on the other side of the world whose language you do not speak, whose face looks nothing like yours — you share great-grandparents, if you go back far enough. The family is real. It is just very, very old.

What happened to all the others who came before them — you will not find them in any grave.