The long-held belief that jellyfish are simple creatures with limited cognitive abilities has been dramatically overturned.  A new study from the University of Copenhagen reveals that Caribbean box jellyfish are far more advanced than previously thought, displaying complex learning abilities despite their rudimentary nervous systems. Not so simple  While jellyfish have inhabited our planet for over 500 million years, their reputation has mostly been that of uncomplicated beings.  This notion has been largely based on their primitive nervous systems, particularly when compared to organisms with advanced centralized...