Klimt's "Couple with cricked necks": Kissing is a learned behaviour the origins of which may be associated with women who chewed up pieces of food and passed them directly into their babies' mouths. This sign of mother-child affection thereafter spread by transference to other relationships. However, there have been and still are non-lip kissing cultures in which food is passed this way. Early Vedic Sanskrit texts apparently (I haven't read them) describe Inuit-like, scent gland-sniffing nose rubbing and pressing, which was possibly a precursor to lip kissing.

Although some Central African tribes find kissing repugnant, kissing is manifest in many different human cultures. Couples often turn their faces to one side or the other when kissing and place their heads at an angle to prevent nose collision. Psychologist Onur G�nt�rk�n, who spent two and a half years as a voyeur collecting data on 124 "kissing pairs" at airports, parks, beaches and railway stations, showed that head turning to the right is twice as common as turning to the left. G�nt�rk�n claimed this phenomenon was the result of neonatal right side preference.