If the first human was truly the only human, would he have mated with his ancestor? Could that happen if they were no longer the same species? If this first human could sucessfully mate with only primates, and his offspring could only mate with primates, and their offspring could only mate with primates- how did they become human? Please advise. I'm confused.
You seem to think that speciation is a clearly defined concept, in which suddenly one generation instantly becomes a different species than the last. That's not the way it works. It's a gradual process, taking many generations. Any given generation is of the same species as its parents and its children, by definition. It just that, over time, it slowly becomes unable to breed with its distant cousins. And, just for your information, humans are primates...