The Family You Don't Recognise

Look at the next stranger who passes. Not a metaphor, not poetry: that person is your cousin. So is everyone on the street, everyone in the country, everyone alive. The only question is how many "greats" go in front.

The arithmetic forces it. Two parents, four grandparents, eight before them — the number doubles every generation back. Go far enough and your ancestor count balloons past the number of people who have ever lived. It cannot be right, and the resolution is the strange part: the branches of your family tree fold back into each other. The same people fill thousands of slots. Everyone's tree does this, until all the trees grow into one tree.

The mathematicians who chase it find that the common ancestor of everyone alive sits only a few thousand years back — not at some single origin, but recently, inside recorded history. The last person from whom every living human descends may have walked the Earth while the pyramids already stood.

The crowd around you is not a sea of strangers. It is a family reunion so vast that nobody recognises anyone.

And if you go back just a little further — does everyone alive share a single mother?