So let me get this straight. At some point in the past neanderthals and Cro-Magnons mated and produced offspring that could in turn be fertile and produce offspring themselves. This has to be case since many if not most modern humans have neanderthal DNA.
Doesn’t that make neanderthals and Cro-Magnons the same species then? How can science classify them as separate species?
Species designation is vague and fraught with guesses, errors, etc. Species are defined not only by reproductive fidelity and success (which we don’t always know), but also geographically and through time.
This is one example of many instances of the impreciseness of science.
Because of longstanding master-race biases.