Everyone, or No One

Run the family tree backward and something strange happens to it. Past a certain point — only a few thousand years back — every single person then alive falls into one of just two groups. Either their line eventually died out completely, and they are the ancestor of no one now living. Or their line survived, and they are the ancestor of everyone now living. There is almost no middle ground.

Genealogists call it the identical ancestors point. Beyond it, all of humanity shares not merely some ancestors but the entire set of them — the same complete cast of great-great-grandparents, held in common by every person on Earth. A forgotten farmer, a famous queen: if their descendants reach the present at all, they reach all of it.

The human family is not a warm metaphor. Far enough back, it is one literal tree, and you hold every root of it.

And if everyone shares the same ancient ancestors — who were the ones that vanished without a trace?