1. Don't we have people who can't pass their driver's test? People who can't read???Certainly, there ought to be a species of monkey that had half-evolved into a man, maybe half as smart as men, maybe able to read and write simple sentences, or able to drive a car or ride a horse?
But there is no such species as a half-man, half-monkey.
True, they have been able to teach sign language to apes, but it takes a great deal of human effort to do this, and you must feed apes constantly to keep them interested.
A human baby does not need treats to motivate it to learn, it is motivated by the learning process itself.
2. We killed off that other species. In fact they were smarter than us but we were bigger and bred faster.