They were simply people, living their lives in the mountains and forests and grasslands of ancient Eurasia.

The encounter that produced Denny was, presumably, simply human — or at least, simply whatever the behavioral equivalent of human was for Neanderthals and Denisovans.

Two individuals from different groups met, in circumstances we cannot reconstruct, and produced a child.

Whether they had anything like the concept of group identity, or whether that identity was as relevant to their interaction as it is to ours, is unknowable.

What we do know is that the biological boundaries between their groups were not absolute.