The natural historian Ernest Crawley wrote that kissing was "a universal expression in the social life of the higher civilizations of the feelings of affection, love and veneration." He also notes that the act of kissing was very rare among the "lower and semi-civilized races." but was "fully established as instinctive in the higher societies."
In modern times, scientists have done brain scans on people when a romantic relationship progresses. Some studies found that after that "first magical or perfect first kiss" a complex system in the brain is activated and flooded with dopamine, an internal chemical that is "released when you're doing something highly pleasurable."
Here is the list of the different types of kisses from Christopher Nyrop, author of The Kiss and Its History: kisses of love, affection, peace, respect and friendship.
Kissing also is found to result in reduction of perceived stress, an increase in relationship satisfaction and a lowering of cholesterol levels. So do yourself a favor and pucker up!