When we began to move out of Europe into Asia, there they were. When we ventured south to where we’d come from, we found them too. These meetings made a sufficiently keen impression on our Stone Age ancestors that they sank deep roots into our mythologies. It is a profound and troubling thing to realize you are not alone. Like us, yet not like us: we remember the people of the forests and the grasslands, the people of the rich, warm lands to which we returned. They fascinated us. They became our elves, our fair folk. The stories we inherited have changed a thousand ways since, of course: nothing is left that could stand as evidence in any court of palaeontology. But our ancestors were still relatively careful curators of their stories. They passed them from generation to generation, and each pair of hands added only a few new fingerprints. We collect them still now, a hundred thousand years later, from across our world. We distil them, boil them down to discover their common features. In this way we can almost remember what it was like to crest the hill and see the fires of the other between the trees.

We speak of them dancing and singing a great deal. That must have been important to them. Or perhaps it was something our own ancestors did not do, until we learned it from the other. We speak of them as frail, slender, ethereal almost. Fragile. Ghost-like in the bamboo forests of Asia, flurrying in hunting parties at the edge of our kin’s fires. Their high, clear voices would lift in chants and choruses after sunset. We remember they were beautiful and fleet and brittle, like glass people, like their music.

We moved south and east, and the others were always a step ahead of us, dancing away into the night. There was some trading—there are stories that have become great legends, of the exchange of impossible things between us and the elusive forest folk. We have tales of questing heroes, travelling to reclaim important things that should never have been bartered away. And maybe there were exchanges of another kind. Genetic investigation certainly suggests that there is a little bit of them in us. Perhaps that tiny germ of code is a key element of what makes us who we are.