The Man Who Knew Everything about Trees

There walked 2 men in the forest and one said " there is nothing about trees that i dont know" the other retorted ahh ok that big tree ahead of us which part is the front and which other part is the back. The knowledgeable man asked if he could walk around the tree. He was given permission and he slowly walked around the big tree. Then he stood at a point and said " I am 100% sure that this is the front". The doubting friend asked how he got to know... and he said there is a big "shit" at the other end and nobody will shit at the front of a tree...People usually hide at the back to do such things.