I was reading Science News and came upon this very interesting question. It took me about an hour to get the answer from what I knew. Now it’s your turn. Answer this question by posting a comment.
UPDATE: Apparently no one knew the answer. See this post for the answer.
There are still monkeys because when the strongest and smartest apes (a long with a little genetic mutation for a boost) began to slowly evolve into humans, they grew more intelligent, by a massive scale.
When other species evolved, however, different circumstances occurred. The more dominant species took over the lesser species, as natural selection proved its worth.
However, as humans evolved, they got more and more smart. This growing intelligence allowed the humans to not feel the instinctive need to remove the lesser species.
Humans realized that apes were not a threat to them, or their well being so thus they allowed them to survive as a species.
Of course, this is changing these days -.-
Plausible… but the answer I’m looking for is a lot less complex than what you’ve written. I’m not saying this is necessarily “wrong”.
I will give people more time to think about this.