Every person who had lived during that period had died, as had their children, and their children’s children, through hundreds of generations.

The world had passed through the end of the Ice Age, the extinction of most of the large animals that had shared the Americas with these early people, the development of agriculture, the rise of cities, the invention of writing, the entirety of recorded human history, and the industrial transformation of the modern world.

And the footprints were still there.

Not because anything about them was specially protected.

Not because someone had decided they were worth preserving.

But because the specific combination of geological circumstances that surrounded them — the fine-grained sediment, the rapid burial, the low-energy erosion — had conspired to keep them intact through everything that had happened in the twenty thousand years since they were made.