The child does not know that we exist.

There is a gulf of 1,240 generations between that child and any person reading these words, a gulf across which almost nothing is preserved except the most durable objects and the most resistant molecules.

And yet the DNA in that tooth survived.

The information persisted.

The molecular record of a child who lived thirty-one thousand years ago was maintained, by the cold of the Arctic, through 1,240 generations of human history, until a sequencing machine in a twenty-first-century laboratory read it and a team of scientists made sense of what it said.

What it said was: we were here.