Manydifferent genes control the manyfeatures of the ears. Selectivebreeding can be used to magnify desired traits. All domesticrabbits are the same species, however, their individual breed traitsvary widely. Rabbits chosen for breeding would have had awide space between the ears and the ones with the longest ears wouldhave been bred together to produce a rabbit with long ears that lop andthat had poor connective tissue development at the base of their ears(allowing them to flop to the side). This trait canalso be noted in other breeds besides lops -- for instance, I commonlysee young erect eared Silver Martens with "airplane" ears.
According to Bob Whitman's book, Domestic Rabbit Breeds &Their Histories, precisely when and where the lop eared rabbitoriginated is unknown. It is speculated that the first lopsmay have been bred in China by the 16th century.
Pam