Although we have precious little definitive scriptural evidence (since that's not what the Bible's about), my sense is that, as you hypothesized, "Yahuweh created a manlike creature lacking a conscience along with the beasts and the like, just to create a different manlike creature later, Adam, replete with a conscience." (I'd characterize the neshama as something more significant than merely a conscience, however. It's our species' unique capacity to host an eternal spirit within our souls---something no animal has.)

It's clear that classical "Darwinian" evolution had nothing to do with this process, since there wasn't nearly enough time in which chance had an opportunity to work---in truth, the theory of evolution was all washed up the moment it was proved that the universe had a beginning. The theory requires near-infinite amounts of time in which to operate, but scientists have pinned down the age of the universe (since the big bang) at about 13.7 billion years, and worse (for the evolutionists) our solar system is only about 4.5 billion years old. Still worse, primitive life showed up immediately after the earth cooled and liquid water condensed to cover most of the planet. And at strategic steps along the way, new life forms---fully developed, with no evolutionary trail leading back to previous species---appeared "spontaneously" on the earth. At the so-called "Cambrian explosion" where we see the first fossil record, every phylum ever extant on the earth is represented there. You'd have to be blind to miss what's going on: Yahweh was preparing this planet for our use, providing an atmosphere suitable for us, soil in which to grow our food, and scavengers to clean up the mess (so no, man-like creatures did not coexist with the dinos).

Proto-man (Cro Magnon, Neandertal, etc.) showed up maybe 300,000 years ago. I'd class earlier creatures like australopithicines as extinct, sophisticated apes. Perhaps I'm off-base here, but I look at these creatures as God's sketchbook---the method He used to decide what physical form He'd like Man to take. But when He decided it was time to "sculpt" His Masterpiece, Adam, He pulled out all the stops, so to speak, making him and Chavvah perfect specimens of the ultimate creature. Then (in Genesis 2:7) Yahweh "signed" His work, equipping Adam with a neshama, the "breath of life." Was Adam a descendent of some earlier form? Apparently not, for the verse cited says "Yahweh Elohim formed man of the dust of the ground..." God didn't start all over again with the design, but He did use a fresh sheet of paper.

Now here's where it gets interesting (and hits a little closer to home): The point of the flood of Noah's day was to wipe out "all in whose nostrils was the breath of the spirit of life" (Heb: neshama) except for Noah and his family (Genesis 7:22). Why? Because apparently the vast majority of those equipped with a neshama had chosen to be indwelled not with Yahweh's Spirit, but with Satan's. If there were still any proto-humans around (and it's quite possible that there were), they wouldn't have stood a chance against these intellectually superior creatures indwelled with demonic spirits. The reason we need to be cognizant of these things today is that Yahweh is not through separating the Ruach Qodesh-filled neshamym from the Satan-filled ones. The Tribulation will see a similar sifting of the spiritual chaff from the wheat.

kp