One upon a time, when we all lived in the forest....

Possibly the only good part about me watching the craptacular movie Knowing last night was that the end got me thinking about trees.
Trees play a big part in old religions. The Norse and Celts both had the World Tree which was the backbone of the world they knew, Judaism and Christianity have the Trees of Knowledge and Life, many Native American beliefs featured trees similar to the World Tree, etc.
But why?
Well, in pre-Christian societies people were living in the last great ancient forests. And those forests featured massive trees. The biggest things some of these people would ever see were the trees around them. And something that big would eventually be revered. The Greeks put their gods on the top of their mountain, and other cultures put the world on the back of a tree.
However, only Christianity retained a literal view of that tree. In Norse religion their Tree is a symbol, and apparently stopped being a representation of a real tree long ago. It is the symbol of the world, and the cycles that the Norse saw in it. The modern druids use their Tree as a symbol of nature. It has gone from being the world to being the symbol of the world.
The tree is so enduring that it still shows up as a symbol of life, even in terrible movies. You see it and we know what it means. Living tree means continuation of life. Dying tree means the end of life.
The fact that everyone seems to understand this speaks to how much in common we all have.