I'll have to disagree. (I don't think Greece is an example of racemixing; virtually all the Helots were White; not as advanced a type, perhaps, as the highest of the Greeks -- who were exceptionally brilliant -- but still White.) Real mixing of widely divergent races brings down the higher type immensely, unrecoverably -- India is a good example of that. Yes, you occasionally get some family lines in India who look mostly White, and even more often you get some genius, but it's not enough to say the race is returning. It would take many generations of intense eugenics to do that. So I'll stand by my statement that racemixing, if quite thorough, threatens to set us back 100,000 years. And that might be enough to kill us, if the comet or energy depletion or other disaster comes sooner than that. If we do indeed have no worries for millions of years, then your idea has merit.