Simplify the following text for a Grade 11 native English-speaking person.
Original: The surface of the cerebral cortex is folded in large mammals , such that more than two-thirds of it in the human brain is buried in the grooves , called `` sulci '' . The phylogenetically most recent part of the cerebral cortex , the neocortex ( also called isocortex ) , is differentiated into six horizontal layers ; the more ancient part of the cerebral cortex , the hippocampus ( also called archicortex ) , has at most three cellular layers , and is divided into subfields .
Simplified: The neocortex is the newest part of the cerebral cortex to evolve ; the other parts of the cerebral cortex are the old cortex , mostly the hippocampus .