"Look, Steve, I'm not Heinrich Himmler. But separated populations of one species over time become separate species"

😁 I know that. I'm just saying that evolution is far more complex than you're portraying it. Yes, some species diverge to the point where they can't interbreed. Others, lions and tigers for example, are still able to breed despite significant time evolving separately.

Yes, it's *possible* that some groups of humans might, after an enormous amount of time and under some currently unknown evolutionary pressure, have become mutually infertile. This is just as likely to have happened within groups of humans we erroneously think of today as the same "race." But I see no justification at all for the certainty with which you made the claim.