ORIGINAL: quiksilver
Animals evolve. I think we've conclusively established that. For example: Due to advances/changes in medicine/nutrition/genetics, humans are getting taller, and our brain size has grown. It's a scientifically proven fact. 4 million years ago, a five-foot tall human with a 500 cc brain cavity was above average. Now, we have an average height of close to 6' with a 1200+ cc brain.
I don't believe we have conclusively established evolution. I would also note that scientist have said in the case of many animals, the size of the brain is not directly related to intelligence. Evolution cannot be directly observed, so therefore it can only be a theory.