Genesis 1:29

"Then God said, 'I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it.  They will be yours for food.'"  Genesis 1:29

So God created mankind and is now telling them what to eat.  Our original food was only plants.  I've heard repeatedly that it's healthier to be a vegetarian and this verse has been used to support that, but meat tastes so good.  My dad was looking at a book that gave advice for heart disease, and that book cited a study where one group ate just vegetables and the second group ate lean meats.  The first group's heart disease was reversed, but the second group saw little, if any, change.  (If I find the name of the book I'll post it in the comments.)

So mankind was given plants and fruit too eat, and was supposed to rule over the animals on the earth.  This is the purpose God gave in the first chapter of Genesis.  We were created to rule. 

If you look at a person and their dog, you often see that if the person is firm and in control the dog is well behaved and happier.  If the person is weak, then the dog is more nervous and less well behaved.  Of course you do have extremes with someone being so controlling and demanding it turns into abuse.  If a tyrant is on the throne he quite often is dethroned before too long-sometimes by his own subjects, sometimes by an outside force.