[TigersEye]

A molar discovered in a cave in Laos shows the enigmatic Denisovans could have interbred with the ancestors of modern humans.

The 'could' in that sentence refers to where the interbreeding might have taken place (at least some of it) not that the interbreeding itself is in question.

They are making an assumption that the cave was an attractive den of iniquity to them. Maybe they found a lava lamp in there too.

[TigersEye]

Somehow I didn't get the full sentence when I copied and pasted it which has the qualifier that makes my point. Doh!

A molar discovered in a cave in Laos shows where the enigmatic Denisovans could have interbred with the ancestors of modern humans.