Not One Link Broke

Consider what it actually took for you to be here. Every single one of your ancestors — not most, every one — survived long enough to have a child. Through four billion years of ice ages, plagues, predators, famines, and wars, an unbroken chain of them, each link a creature that lived just long enough to pass life on. The instant any one of them had died childless, the whole line to you would have ended, and you would simply never have been.

You are the living tip of the longest winning streak on Earth. Not one of your forebears, across billions of generations, was a loser in the only game that counts. It is a kind of miracle written into the fact of your existence, and it belongs equally to every person you will ever meet.

And yet the chain came horribly close to snapping. More than once, the whole of humanity dwindled to a frightened, fragile few.

And if the chain nearly broke — when, and how close did it come?