The Strangers in Your Blood

She had neighbours. That is the part the story always forgets. Mitochondrial Eve is real — a single woman whose unbroken line of daughters reaches every living human — but she was not alone, and she was not the last of her kind to matter. Around her, and for hundreds of thousands of years after, there were others. People who looked almost like her. Who built fires, buried their dead, made things with their hands. They are gone now, in the way that matters for counting — no living human descends from them down an unbroken mother-to-daughter chain. But gone is not the same as vanished without a trace.

Because they met. At the edges of ranges, in valleys, along coasts — they found each other, and some of them had children together. And those children survived. The proof is not in a story or a fossil. It is in you. A stretch of your DNA, right now, came from a human who was not quite the same kind of human as you. If your ancestors ever left Africa, somewhere between one and four percent of your genome was written by someone we call a Neanderthal. Another fragment, smaller and stranger, came from a people we only discovered through a single finger bone found in a Siberian cave. We named them the Denisovans, and we are still not sure what they looked like.

Evolution did not pick one winner and erase the rest. It made a palimpsest — old writing showing through beneath the new.