I believe the first and main reasons for animals were for food and helpmeets. Man needed animals on small farms to survive. In time man took some strictly as pets and companionship beyond what a wife and family provided. I think all of that will be different and/or not even exist in the new Earth.
If the first and main reason for animals was for food, why did God not create just farm animals? What are birds for? What are fish for? Why is there such an abundance of variety of animals that humans cannot make use of? And why did God forbid to eat certain animals, why are some unclean? You know how well pigs are suited for food, why did God not allow it if He created animals for food?
Then look at Genesis 2:19. It says of God after He created the animals:
"He brought them to the man to see what he would name them; and whatever the man called each living creature, that was its name".
The first thing God does after creating the animals is making sure they are
named. Naming something applies
value to it. Adam didn't name the plants, but the animals. Plants were for food, but the animals were named. God didn't create the animals to be mere food only.
Next take a look at Genesis 7:
God saved 8 people from the Flood, but thousands of animals. Not a single animal went extinct by the Flood. That's how important they are to God. If animals were just for food, why would God let Noah work so incredibly hard building a giant boat and feed
all animals for some 310 days, instead of just letting him deal with the "important" ones, the farming animals?
Paul wasn't talking about animals in that verse. He was speaking of all of creation in general not specifically created animals. ie: the old Earth groans to become the new Earth...non-literally.
Let's read it together:
"For the earnest expectation of
the creature waiteth for the manifestation of the sons of God. For
the creature was made subject to vanity, not willingly, but by reason of him who hath subjected the same in hope, Because
the creature itself also shall be delivered from the bondage of corruption into the glorious liberty of the children of God. For we know that the whole creation groaneth and travaileth in pain together until now. And not only
they, but ourselves also, which have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, to wit, the redemption of our body."
I don't manage to see "the creature" as plants or rocks. In the Bible "creatures" are always humans and animals.
It also says "not only they, but ourselves also, which have the firstfruits of the Spirit". Does this sound familiar? This is referring to Genesis 1 where the Spirit is the difference between man and animal. In other words: "not only the animals, but also we who are only different because we got the Spirit".
Eccl 3:19-21
19 For that which befalleth the sons of men befalleth beasts; even one thing befalleth them: as the one dieth, so dieth the other; yea, they have all one breath; so that a man hath no preeminence above a beast: for all is vanity.
20 All go unto one place; all are of the dust, and all turn to dust again.
21 Who knoweth the spirit of man that goeth upward, and the spirit of the beast that goeth downward to the earth?
KJV
Man's spirit goes up to heaven, but the spirit of animals go downward. It's God's way. I trust that God knows what's best.
The only mention of an animal in the eternity chapters of Revelation is the Lamb, which is Jesus Christ and not a literal lamb.
Here is what my Bible says (Ecc 3:19-21):
"Surely the fate of human beings is like that of the animals; the same fate awaits them both: As one dies, so dies the other. All have the same breath; humans have no advantage over animals. Everything is meaningless.
All go to the same place; all come from dust, and to dust all return. Who knows if the human spirit rises upward and if the spirit of the animal goes down into the earth?"
Do you notice how the last sentence is a question and not a statement? All go to the same place, and we're not entitled to decide which spirit goes where.