>>8470
Well, I don't think TES even has theories of racial evolution the way we think about them. Each race just kind of has their own myth of how *they* came to be, might mention the few other humanoid races, and if you don't fit in then you just don't get mentioned and we don't know how you came to be. This is the case then for goblins and trolls. They just… are.
I mean, we know trolls are intelligent enough to write letters, perform basic manual labor and have a Daedra give a shit about them, so there's that. Goblins and reiklings are smart enough to have basically tribal societies with structure, shamans, rudimentary religion (which we don't know much about), etc.
Heck, look at dreughs. They are or were intelligent enough to be the dominant race on Tamriel in a previous Kalpa, and now they are just another set of mooks.
The lines between elven and manish are difficult to discern when we're talking about non-playable races. Giants, for example, I imagine some people thought that they were closer to the elves due to their ears, but more recent lore seems to suggest they share common ancestors with the Nords of Skyrim. If there's any race the goblins, trolls and ogres are close to, any of the civilized races I mean, It would be the Orcs, whom in turn may come from elves ( that's the belief that holds most water since Morrowind added them as a playable race).
I wouldn't place to much stock on the black soul/ white soul situation as that's just more game mechanics than anything else. I would imagine that all souls get recycled into through the dreamsleeve, as it seems like they are a finite resource that cannot fully be created or destroyed but only re-organized or trapped away, by Daedra or the masters of the Soul Cairn.