Yeah, that's a little more tricky. Obviously there were other humanoid creatures that existed somewhere along the timeline. I've always assumed these fit into the evolutionary process. I don't think mankind was any different in this respect than the rest of creation. I don't really buy that Adam and Eve were just put there one day, ready to go straight out of the box. The Bible says they were, but again, it was likely a recording of a story that had been passed along for some time, based in legend more than science.
That's my long version of "I really don't know..."
My own opinion on this is kind of close to that--Adam and Eve's bodies were likely created through an evolutionary process. But as I see it the main difference between Adam and Eve and hominids prior to them lies in the plan of salvation description I gave above--humans are literally spirit children of God, and partakers in salvation through Christ. So, to my view, the hominids prior to Adam and Eve did not know right from wrong, could not sin, and had no need of an atonement. So in that sense, Adam and Eve were an abrupt change with what had existed previously.