How brain components evolve

The parts of the brain can evolve independently from each other. The brains of approximately 10,000 mice were analyzed. Seven individual parts of each brain were measured by volume and weight.

Brain components evolve separately and not together as one single unit.

http://news.bioscholar.com/2012/09/brain-parts-evolve-independently-study.html

That's why I think, when a person has problem in his brain, surgeon cut off a part of his brain.