If there is a "debate" here, it may only be over definitions of words -- what, exactly, is a species, sub-species or 'racial sub-type'?
Consider that horses and cows cannot reproduce, period, so by any definition, they are separate species.
Horses and donkey's produce mules, which themselves cannot reproduce, and so again by definition, the parents are also separate species.
But now consider various "species" of, say, zebras (Plains, Mountain & Grevy's) which can produce viable offspring -- and yet they are still considered separate species.
So the question is, by what definition?
If different species can produce viable offspring together, then how are we even calling them "species"?
The same would hold true for pre-human species, of which the fossil record identifies nearly two dozen.
Were some of them biologically close enough to have produced viable offspring?
And if so, why are we still calling them separate species?
Correct. If two groups can mate and make viable offspring, they are the same species (or that is the old way of viewing things).
Part of the reason we have some many species is it helps get your paper published.