I have heard stories/reports that if a certain part of the brain (taking care of certain functions) is damaged other parts take over the function of the damaged part.
Intuitively this could mean 2 things:
We are not using the brain to its full capability.
The performance of the brain will take a hit due to other brain centers taking over the functionality of the damaged center.
For me the first one does not make sense since evolutionary selection makes sure we are endowed with the most efficient systems. So what is happening exactly when brain centers get damaged?