Denny’s 50-50 proportion is consistent with exactly one thing: she is the direct F1 offspring of a Neanderthal and a Denisovan.

Not the grandchild.

Not the great-grandchild.

The direct child.

There is no other interpretation.

The proportion rules out anything else.

This is why the discovery was so striking even to scientists who had spent years working with ancient DNA and who were accustomed to thinking about ancient human interbreeding as a general phenomenon.

They had always been working with the diluted echoes of ancient encounters.