Evolutionary advantages of backwards brain?

My professor said that human brains are in "backwards" because the vision center is in the back and the left and right hemispheres are reversed in terms of what body parts they control. You'd have expected that the correct orientation for a brain is left hemisphere matched to right side, left to left, and vision center right behind the eyes. So it is like someone reached into our skulls and turned the brain around. He said that there must be an evolutionary advantage because this is true for all animals. (1) Is it true that it is reversed for all anmals? (2) What is the evolutionary advantage for reversing the brain? I tried google, but nothing shows up. Oh, this is an extra credit question for a summer class. I could really use extra-credit.