As vertebrates evolved, the increasingly complex structure of the brain conferred increasingly complex function, especially apparent in the . View Available Hint(s) As vertebrates evolved, the increasingly complex structure of the brain conferred increasingly complex function, especially apparent in the . sleep-wake cycles of birds and mammals cerebral cortex, which is greatly expanded in nonhuman primates and cetaceans forebrain, which is a small brain region that arises early in development brainstem, which in most vertebrates, controls homeostasis and basic bodily function medulla oblongata, which controls automatic functions