Hey guys, last night as I was lying in bed I had this crazy thought. It's a rather far-fetched theory, and there's really not much evidence to support it, but hopefully you'll find it an interesting read nonetheless. So here goes:
Azeroth has numerous Wild Gods, as well as several sapient animal-based races commonly associated with said gods. There's Ursoc and the Jalgar/Furbolg, Niuzao and the Yaungol/Tauren (presumably), Agammagan and the Quilboar, Aviana and the Harpies, Tortolla and the Tortollan (presumably, if the latter is to be considered canon), and possibly more. Brann Bronzebeard theorizes that these races descended from their respective Wild God in one way or another. Then there's also the Worgen, who share a connection with the Wild God Goldrinn, but their relationship with this god is different from the aforementioned races if Brann is to believed... But what if Brann is wrong?
The Worgen were created by Night Elf druids as a shapeshifting form by drawing on the powers of Goldrinn and as a result they also adopted his fury and savagery. Many Worgen became feral and hostile, unable to shift back into their normal form, and in most cases it took special druidic intervention to just partially revert the effects and allow the Worgen to regain their sanity. Most of the non Gilneas-related Worgen we meet in the wilds of Azeroth are still lost in their rage, more beast than man.So what if the other animal-based races had a similar origin?
Because they draw on the power of Goldrinn, the Worgen became wild and ferocious (like Goldrinn). Tauren are calm and centered, similar to Niuzao. Agamaggan was said to be noble but he was also shown wielding great fury; Quilboar are similar. In fact, all the Wild God-related races are shown to possess traits found in their respective god. It is of course possible they inherited them when they "descended" from them, but perhaps they gained these traits by drawing on the powers of their respective Wild God, similar to the Worgen and Goldrinn.
As we all know, Malfurion was the first druid, having been taught druidism by Cenarius just prior to the War of the Ancients. Malfurion passed his knowledge on to other Night Elves, which would eventually lead to the creation of the Worgen. We also know from Chronicles that Cenarius lived among the Yaungol decades before teaching druidism to Malfurion. So how can the Yaungol/other Wild God-"descended" races possibly share a similar origin to the Worgen? The answer is simple: Trolls.
Trolls worshiped the Wild Gods, or Loa, long before Night Elves or druids were even a thing. Trolls were never taught druidism by Cenarius, but still managed to learn druidic magic (or something closely resembling it) on their own. Similar to druids, they learned how to draw on the power of the Wild Gods, and how to transform into shapes resembling them. So basically, various groups of Trolls drew upon the powers of specific Wild Gods, turning into forms resembling them, and slowly over time became different races altogether through the power of these Wild Gods. This would also mean that Trolls were (potentially) the only sapient specie to naturally originate on Azeroth, with all others having either evolved from them or from the Titan-forged.
Now, here's how this theory "starts" to fall apart:
The Worgen weren't just created by drawing on the power of Goldrinn. It also took a certain artifact; the Scythe of Elune. Without it, the Druids of the Pack as they were called simply resembled ordinary wolves, similar to how Druids of the Claw transform into ordinary bears etc. Additionally, unlike other druid forms before them, the Worgen also had great difficulty (or unwillingness?) to turn back to their normal forms, perhaps from the effects of the Scythe's interference. From what we've seen in-game, Trolls are able to transform into animal-humanoid hybrids (akin to the Worgen) when drawing on the Wild Gods' powers without the need of an artifact like the Scythe of Elune (as seen in the Zul'Gurub bosses), but from what I recall they've never been shown having difficulty reverting back to their normal form or being permanently transformed. It is, however, possible that they could've used similarly powerful artifacts that prevented them from transforming back when they allegedly became the various animal-based races. Or the magic used could've been more potent that modern-day transformations.
Finally there's also the issue of the 'Worgen Curse', and how the Worgen form could be transmitted to others, which isn't an ability any of the other animal-based species share. It's also not an ability any of the other druid forms share, so perhaps this is also a result of using the Scythe. If the Trolls used artifacts of their own to create their forms, perhaps the curse is a side effect specific to the Scythe? Alternatively, it could also be the subtle differences in Troll and Night Elven druidism that resulted in the Troll forms not having a curse associated with them.
Well, that's pretty much it. Like I said, this theory is rather far-fetched, but what do you guys think? Is there some sliver of plausibility to any of this?
TL;DR Quilboar, Tauren, Furbolg and all other sapient species native to Azeroth with ties to the Wild Gods actually evolved from the Trolls, quite possibly making Trolls the only race to have naturally originated on Azeroth.