I think it highly likely that some interbreeding occurred. The problem with anthropologists is that they tend to see evolutionary progression as a one-dimensional thing, i.e., X led to Y which led to Z and so on. For X, Y, and Z they have only the particular species that have been discovered, not the plethora of transitional forms in between, which may have numbered in the hundreds and consisted of types whose differences were so minute as to be undetectable. The same thing applies to history. There's a tendency to see everything moving in a linear progression with no interaction or branching-out involved. The untrained historian sees, for example, the Babylonians, the Assyrians, the Egyptians, the Greeks, the Hittites, each in its own context, without really understanding that there was continual movement of all these peoples, inside, outside, and upside down, and continual interaction between them.
Amen. Well stated. It's like trying to track race using linguistics.