I wrote the rest of this post down on Friday and meant to post it this week. But then i checked YouTube today and discovered that the new season of Epic Rap Battles of History just started, and the first video is George R R Martin vs J R R Tolkien. And it is awesome. Enjoy!
If you remembered to come back from the video, this is my interpretation of the Middle-Earth creation mythos:
Eru, to the other gods: "Despite some initial unpleasantness we've got the world mostly worked out now and filled with plants and beasts, so we should get down to the important stuff, the sentient races. Since I'm the firstest and bestest of the gods i shall create the Elves, and they shall be the Firstborn."
Aule: Uh, when exactly were you planning on doing that?
Eru: I don't know, I figured I'd get around to it sooner or later. Maybe another couple Ages. No rush.
Aule: So, uh, i already kinda created the Dwarves.
Eru: Damn it! I'm first! I get the Firstborn! I'm not going to grant your dwarves sentience until _after_ I've created my Elves! Go stick them in the freezer for now or something!
Manwe: Would this be a bad time to mention the Eagles I made? Cause i thought it would be cool if there were giant sentient Eagles.
Eru: Eagles aren't real people! They don't count! In fact maybe I won't even give them souls, that'll show you! But stick them in cold storage for now just to be safe and we'll figure it out later. AFTER the Elves are created!
Yavanna: So about that... I can already tell Aule's Dwarves are going to be trouble, so I made Ents to protect the forests from them.
Eru: What is wrong with you people?!? You can't just go around creating races willy-nilly! That's my job!
Yavanna: It's Aule's fault for creating such a stupid race first!
Eru: Fine! Whatever! The Ents are going into cold storage with all the rest! They can just be trees for now, and the Elves, the FIRSTBORN, will wake them up AFTER I'VE CREATED THEM FIRST! Because THEY'RE THE FIRSTBORN!
[Tom Bombadil wanders in from somewhere]
Bombadil: They're first? But what about me? I'm here, I'm Eldest, I've already seen the first raindrop and the first acorn, so technically...
Eru: ARRAAARRRAAAGHHHHHHH!!!!!! *retroactively smites Tom Bombadil from existence
And that children is why Tom Bombadil did not appear in the Lord of the Rings movies.
1: The bit about the Dwarves and the Elves seems to be generally accurate. Information about the nature and origin of Ents is vauge, the information about the Eagles is even vaguer, and the information about Tom Bombadil is vaguest.
2: Ainu, whatever.
3: "Years of the Lamps" (https://en.wikipedia.org/wiki/History_of_Arda#Years_of_the_Lamps)
4: I'm sure steuard will correct me on all the whatevers.