Young Kissing Girls

Within the natural world of animals there are numerous analogies, notes Crawley, such as "the billing of birds, the cataglottism of pigeons and the antennal play of some insects." Even among higher animals such as the dog, cat and bear, similar behavior is noted.
Types of kisses
Christopher Nyrop, in his book The Kiss and its History (1901), identifies a number of types of kisses (kisses of love, affection, peace, respect and friendship), while noting that the categories were somewhat contrived and overlapping, and other cultures often had more kinds, including the French, with twenty and the Germans with thirty.