But the specific number, the specific frequency of such encounters, remains uncertain and is likely to remain so with the available methods.

What can be said is that such encounters were apparently not impossible — and that when they occurred, they could produce children who were part of the ancient human world in their own right.

The Question Of Language And Culture

One of the most enduring mysteries in ancient human evolution is the question of language — of whether Neanderthals and Denisovans had communication systems comparable in complexity and flexibility to modern human language, or whether modern human language was a unique development that gave Homo sapiens an adaptive advantage that other ancient human groups lacked.

The fossil evidence on this question is frustratingly indirect.