While we’re talking about the corpus callosum, it should be noted that restricting intelligence to the performance of one piece of your brain is… dumb. That would be like saying that your car goes faster because it has better spark plugs. Spark plugs certainly help, but they are certainly not the be-all-and end all of the car. Peter U. Tse of Dartmouth observes that Einstein’s corpus callosum is large for a man of 76, his age at death, but it’s not much larger than a young person’s. “It might just be that Einstein's brain was more like a young person's brain in that sense.” In this way, intelligence may be considered a use-it-or-lose-it proposition, and Einstein may just have been “Mr. Universe” in the way he worked out his brain.
This one's for the ladies!