I have to begin by saying that I am no biologist or anthropologist or even an exceptionally well learned amateur. These are just opinions that could serve as plausible explainations, and are just food for thought. But, don't discount me because of that. I have as much authority on the subject as the average preacher who claims to have all the answers to life and our origins, and i claim no such thing.
to OP: evolution happens out of necessity. The apes did not evolve into "semi-humans" because they didn't need to. Or maybe some apes are "semi-humans" in a way. Studies show that apes can be relatively smart, but they probably didn't come into their own due to the fact that they don't need it. Why did early humans feel the necessity for more? They could be the great-great-great-great (etc.) grandchildren of the smartest proto-humans who may have had an instinctual drive to hook up with the smartest of the bunch. Thus, through time we got smarter and smarter and blah, blah, blah. The apes never developed this kind of drive because they are essentially retard-spawn of our ancestors (too dumb to become human, but too smart to just die off). But I have no real clue. This is more of a partial thought than an actual theory.
1. I have a feeling that this sites evolution overview is half-assed. 2. evolution does either happen out of necessity or because certain traits, while not necessarily required for survival, do make survival easier.
example: do you think birds developed wings (let's assume THEY developed them and that God didn't give them to them) because it makes it easier to flee predators and migrate (don't ask me how it happened, i'm no biologist) or because they thought wings would be pretty cool looking?
oh, and i have another answer to the "why no human apes" question: See Africa for that which you seek =)