If a tree fell in a forest...

There is that age old philosophical question, "If a tree fell in the forest and no one was there to hear it did it really fall?" This is kind of a rudimentary question. Because what you are really asking is the effect of sound waves on human organs. But if you look a little deeper you will find yourself asking, "Without us does the forest exist? or the universe?" or a little further, "Is intelligence a prerequisite for existence?" Well what is intelligence? In the case for a forest to exist, you need trees and for trees to exits, you need a ecosystem. Animals, is not animals a example of intelligence? But animals and insects survive on instinct. Is instinct the same a intelligence? In my opinion instinct is action without thought. And intelligence in action with thought. In that light, no intelligence is not prerequisite for existence. Then again, if we as human are not there who really cares.