For the sake of this thread, ignore religious beliefs and accept the theory of evolution. So what would the major Trek races be evolved from? Is there enough info in Trek lore to even answer, or would it all be speculation?
It would all be speculation. It would be species native to their homeworlds that we the audience haven't seen and for which there's no terrestrial analogue.
Somewhere on Vulcan, there are apes with pointed ears and can do the nerve pinch thing. On the Klingon homeworld, there are ridged-forehead gorilla like creatures that act more like rabid chimps.
^:x Trek gets evolutionary history less right than it does particle physics. Anyway, of course pretty much everybody in the Trek universe is going to come from recent ancestors that are more or less physically analogous to primates, because--well, look at them, they're physically analogous to primates. What would be interesting and fun is to construct a plausible evolutionary path and functioning biosphere for beings like the Horta.
If you go by TOS, each planet evolved separately and, because of Hodgkin's Law of Parallel Planetary Development, ended up looking very human, and with surroundings that mimicked almost exactly the Desilu backlot. If you go by TNG, it's the Preservers.
^um... the Preservers is a TOS species. The Preservers were never mentioned on TNG. The aliens responsible for the whole thing in The Chase was never named.
We don't really know what the conditions on the surface were like. The Horta might have begun there, but there were bigger and badder things about and the Horta started digging burrows and tunnels ... things progressed from there.
The Preservers were established as the universal evolutionary origin in TOS The Paradise Syndrome. Wasn't there an early draft of the script that did establish that humanoid was a Preserver? I know, it never made into the show and therefore is not canon.
^^I don't remember Smurfs having ice powers. Or did those develop later on in the evolutionary process?
The thing about Horta is the existence (or not) of an actual food supply. Just because they're silicon-based doesn't mean they can eat sand any more than it means because I'm carbon-based it means I can eat diamonds. Whence the energy? I like to think they get by predation on primary producers that run their metabolisms on uranium. I would say they just run on uranium they find in the rock, but that doesn't provide much selective pressure for intelligence.