No, some subpopulation of prehuman, apelike creatures somehow is isolated from the rest of the population. The gene pool of that isolated group becomes different from the rest of the group. It becomes different enough that the separated group can no longer interbreed with the rest. At this point, a new species of prehuman, apelike creatures has formed. This new species is just a little more human-like than the original group. This happens repeatedly (we see a whole lot of different prehuman species in the fossil record, each of them a little more human-like.) and eventually one of the subgroups is what we would call human.
Isn't this what I said?