As every school-boy knows - The Tree of Life has been use as a symbol in mythology for thousands of years before it was adopted in Genesis, meaning beginning. It is part of ledged and folklore as are many Bible stories written by people who were not born at the time they wrote their accounts of what happened, and had no witnesses, reference books, scrolls, or even google to consult. That’s one neat trick!
As far as I know the Earth originally had no atmosphere containing oxygen. All the air we breathe has come from trees converting Carbon dioxide for hundreds of millions of years. Naturaly the tree is seen as a symbol of life, as without trees we would not be here. If don’t Adam & Eve it, why not look it up.