Creating homogeneous world

In many fantasy stories we encounter races like elves, dwarves and orcs, for instance. We also encounter a pantheon of gods that had a hand in creating these races.

Even if you buy into "creationism" and for the sake of fantasy world building we have to, some things, like language, usually evades said creationist rules. Why would a group of gods create a world and then toss species about as if they want to pin the tail on a donkey, each with their own culture and language. Sure, it helps if you can say that this country is more dark ages Britain (not that there was such a thing) and that country is more renaissance Italy, but does it make sense? No, not really, not even if you tie my hands behind my back, blindfold me and spin me around, the only result you will get is projectile-like vomit.

If the world was created by a group of gods, sure they could have decided that a specific group of people spoke language A, and another one language B. In order for either speaker to communicate with the other, they would have to stand on equal ground, linguistically speaking. Enter the ominous Trade or Common Tongue, a cheap ass short cut ignoring the inherent problem.

First off, why would the gods create multiple different cultures with different languages? Sure, they are gods and can do as they please, and yes, puny humans like us will never understand the mind of gods... unless, of course, we take a step back and look at it logically. A bunch of deities first creating the entire world, their sandbox so to speak, then set out to create their people... so far so Greek. But this is where logic bites the Common Tongue's and the differing cultures' ass! If one group is responsible for creating the world, why the fuck would there be different cultures, who not only speak different languages but behave differently than the core peoples and possibly worship different deities?

Sure, we as writers try to stick close to what we know from our world, so we get nations like Dark Age Britain (which did not exist as a nation) renaissance Italy and post-modern France merrily living next to each other... because the world's creator (aka the writer) thought it might be interesting, and because that sort of stuff also happened in D&D. But if you look at mythology, none of these myths actually deal with different pantheons and stuff. There are no language barriers in the Iliad, the people all speak Greek, they all worship the same gods.

From a purely logical standpoint, a bunch of deities will cobble together a world and people it with their folks and be done with that process. Why would they do more? And no, "because it fits the story," or "because I need a different culture" makes no sense in regards to the internal logic of the tale. If the Greek gods had created the world, every fucking person would speak Greek and worship the same sodding deities and maybe travel to Mount Olympus once in their lives. Because, you know, the Greek deities created the world. Well, the gods came later, technically, but you get the gist.

D&D worlds aren't that good a role model when it comes to creating your own world, Terry Pratchett's discworld is a much better example at creating your own world because it is purely founded on mythology. (Yes, there was a time when the world was flat and all that, at least in the minds of the people.)

Taking our world, aka Earth, as an example for a fantasy world doesn't really work, because, well, history. Each culture had their own gang of gods, their own language, their own way of dealing with strangers... with each culture comes another tale of how the world was created, and since we are dealing with gods that are "real" the powers they give their most devout are also "real." Well, at least some of them have real powers, because, you know, the other gods cannot have created the world. Unless, of course, you have a bunch of godly gangs coming together and in a moment not so unlike Grease, they sing some nonsense and each gang creates their own culture and then the push and prod until the lands fit together atop the giant turtle swimming thru the ether. Or some such thing... problem then is: humans and faith, I mean look at our pitiful existence. For the past 2000 years monotheistic religions have monopolized (see what I did there) their sole truth, slaughtering others and one another in droves.

(Disclaimer: I am not attacking your delusion... err... religion (okay, now I did attack it) but trying to make a point!!!)

The pantheon religions of ancient times never really fought over their faiths, they just adapted what they liked and moved on. Problem is: they are as real here as any other religion... in a fantasy world, they are real!

If you design your world, make it logical. One pantheon/religion, one language with a multitude of dialects, and one "stock" of people (if the elves came before the humans, they still will be of only one "stock") It is the only thing that makes sense.