Books dwindle while AI is entrusted with storing all data. Interesting scenario if all data got lost somehow without any chance of data recovery..

This is a scenario I explore in my story Asimov's Ghost, I am just about to post the long awaited Chapter 6 :-)

This again leads to overdrive of certain parts of the brain yet inactivity of others, making them rudimentary like a whale's feet.

If you haven't already, you should read V.S. Ramachandran's books The Tell Tale Brain and Phantoms In The Brain, I can't remember which one is the second one he wrote, but that's the best one, though they are both worth reading.

I like your theories, you've set me thinking . . . :-)

Cg