What I am saying at the 200,000 year rate you could only have 7500 levels.
Sure. At the bottom level, though, you'd have 2^7500 different species.
It's all but impossible to imagine how many species that is. That's more species than there are atoms in the entire visible universe. That's more than the number of atoms in 100 visible universes exactly like ours.
Is it really so unreasonable to believe that
Homo sapiens would be just one of those species? I don't see that it is. It's more unreasonable to believe that
Homo sapiens wouldn't be one of those species.
Then when they started to mate you have the added problem of mating.
Sexuality, as near as we can tell, emerged quite early in evolutionary history, so I don't see how it's a problem. We have so many sexual organisms because they're all the decendants of the first sexual species, not because they all evolved sexuality independantly. (It's possible, now that I think about it, that sexuality may have evolved two or three times independantly, since there's at least two or three different chromosomal schemes for sex determination that we know about.)
That problem had to be solved along the way somewhere.
It's not a hard problem to solve. Consider a genetic factor that's passed on only 50% of the time. If you have it, you're Sex A. If you lack it, you're Sex B.
Of course, that's not the only way to do it. You can have more than 2 genders, and many species do. But specialized sex structures and body types come long after the genetic basis for sex in evolutionary history. It's interesting but it's not a major problem.