The human brain evolved from the primitive to the complex. The most primitive instincts for feeding, fighting, fleeing   and fornication are found in the deep structures of the  “Hind brain”,  or R-Complex (Reptilian complex).. The Mid brain (limbic system) is at the level of development of a puppy. The warm and fuzzy emotions are characteristic at this level, cuddling and cooing, reveling and grieving happen in the Limbic system.  Then the thing that makes us human, the neo-cortex, (New Brain) responsible for  logic,abstract thought, and all other higher level functions is wrapped around the whole mess in a layer just 3 or 4 centimeters thick..