There are two reasons for that craving for contact. The safest period of our life which our automatic nerves remember is the fetal period during which the contact of the child with the womb is constant and in perfect relation to the fetus' growth.
Also, contact facilitates the electrical exchanges between human beings, especially between male and female, exchanges which owing to the removal of organic inhibitions, must be singularly powerful between lovers.
=Holding Hands.= Whenever conditions separate their bodies, lovers generally revert to the childish practice of holding hands, which to the child meant an assurance of safety when led by the strong parents and also facilitated electrical exchanges of distinct value to the young and old alike.
=The Kiss.= This brings us to the consideration of a love manifestation in which sensations of a tactile, gustatory and olfactory character are combined: the kiss.
The kiss, curiously enough, is found both in certain animal and human races but not in all human races.
Many mammals, birds and insects exchange caresses which remind one of the human kiss. "Love birds" seem to spend much of their time kissing each other.
On the other hand, Eastern races do not seem to relish the caress which Western peoples call a kiss. In China a form of affectionate greeting corresponding to our kiss consists in rubbing one's nose against the cheek of the other person after which a deep breath is taken thru the nose with the eyes half-shut.
In some primitive races the equivalent for our "kiss me" is "smell me." In other races, the kiss is a manifestation of respect rather than a proof of love. Anglo Saxons on certain occasions kiss the Bible. In the early Christian and Arab civilisations, the kiss was a ritual gesture and has remained so in certain Catholic customs: kissing the pope's foot, relics, a bishop's ring, etc.
In certain races, kissing is a proof of affection but not of love. Japanese mothers kiss their children but Japanese lovers do not exchange caresses of the lips, according to Lafcadio Hearn.
The dark races of Africa are ignorant of that caress and so are the Malays, the aborigines of Australia and many other primitive tribes.
=The Birth of the Kiss.= It appears that even among the kissing races, the kiss is a relatively recent development. It is rarely mentioned in Greek literature. In the Middle Ages it was a sign of refinement, being almost unknown among the lower classes.