If you want to simplify the fact about why God put the tree in the garden, think about this. God gave Adam and Eve everything on Earth to enjoy.
Is this the same shortsighted god that couldn't even figure out on his own that Adam needed an Eve?
If you were God and gave man and woman everything to the eye on Earth freely, how would you know they truly were appricitive of the gift?
Are you telling me you can't give your kids something and tell if they appreciate it without threatening them with something else? Somehow I've been able to appreciate the good in things without having something else withheld. What a warped view of life. I once met someone for lunch, someone I really had never known, and they bought my lunch. I thought that was awesome even without them holding another meal for me at another restaurant that I wasn't to partake of. I mean really, does this make sense on any level?
Man through the centuries proven they can't get along without God.
Actually man has proven through the centuries that having god makes them fight and kill each other.
If you ask a kindergartner they would tell you the answer: Just stop fighting Wars and stop harming each other.
Will you kindly tell your god the same so that he doesn't have to slaughter everyone? Or are kindergarten kids more moral than him?