Michael Castleman briefly covers the history and mystery of kissing in this article from PsychologyToday. Kissing is something often overlooked in sexology resources, though it is an important part of intimacy and sex. People have complained that a lack of kissing from their partner has adversely affected their relationship and in some cultures kissing is considered too intimate for public display. Kissing is also something that has evolved over the years, with the first recorded instance of it coming from Sanskrit texts dating back to 1000 B.C. Greek literature also mentions kissing, but suggests it was practiced less frequently than it is today.
Read the full article here: The Mystery of Kissing