I think it already existed Jinx.

Just part of the way things are and no one has a perfect explanation, even the bible doe not give one. But there is good and there is evil, it's just the way it is. Part of the universe or whatever was before even the universe existed.

I could be wrong but I think the 'tree' represents a persona, something other than a tree like an apple tree. Because the tree of life refers to Jesus, God, his spirit etc, life and eternal life. So the other tree probably represents evil in much the same way, call it satan or the serpent, death, whatever you'd like. And they ate from that tree, spoon fed so to speak. lies whatever... in the NT Jesus says... this is my body eat of it... that line got him into quite a mess with his own disciples but it's relevant to the tree of life, the tree of death, the trees of good and evil.

choose a spoon I guess. good or evil. life or death. choose nothing and death claims you.