The story of Denny has captured public imagination in a way that few scientific findings in paleoanthropology have managed, and it is worth reflecting on why.

Part of the appeal is simply the improbability of the finding.

In a fragment of bone smaller than a finger, scientists found the direct genetic evidence of an event that happened 90,000 years ago — an event so specific, so intimate, and so unexpected that it reads like the plot of a science fiction story.

Two ancient human species, whose lineages had been diverging for hundreds of thousands of years, met in the mountains of Siberia and had a child.

That child died young, her bones eventually preserved in a cave, and thousands of centuries later the fingerprint of that meeting was found in her DNA.