Why do we kiss?
The scientific study of kissing is known as philematology. Research shows that a variety of different muscles are used including facial and postural.
The orbicularis oris being the main skeletal muscle involved. Simple kisses use as few as 2 muscles and burn only 2 to 3 calories, whereas passionate kissing can involve as many as 23 to 34 facial muscles and 112 postural muscles. The act of kissing consumes between 5 and 26 calories per minute.
During kissing, couples exchange an average of 9 mL of water, 0.7 mg of protein, 0.18 mg of organic compounds, 0.71 mg of different fats, and 0.45 mg of sodium chloride. As many as 10 million to 1 billion bacteria representing 278 different species may be exchanged during an active kiss, with 95% of these organisms classified as nonpathogenic for individuals who are immunologically competent.
The evolution of kissing begins with primates creating the original baby food by first chewing it and then spitting it into the mouths of their offspring. Overtime kissing became a way to pass on biological information about healthy of the potential mate, as well as a bonding ritual, with the goal being procreation and continuity of one’s genes.
With the kiss partners are able to get close enough to each other to assess essential characteristics about each other, none of which are consciously processed. Although the vomeronasal organs which are considered vestigial organs in humans are responsible for the detection of pheromones, research does indicate that we do communicate with chemicals.
In a research study women smelled t-shirts of various men and pick their favourite. What was found was that the choice the females made was based on histo-compatibility complex (MHC), specifically the more different the genes were the more likely the women were to like the way the man’s shirt smelled. This is relevant because the more different the genes of mates are the better the potential for healthy offspring.
Women are far more choosy than men in terms of partners, and it is theorized that the reason for this is that women were looking for a healthy partner to have offspring with and protect and raise their children. Kissing allows a woman to check for immune and genetic compatibility prior to investing time or energy.
Research finds that most men will have sex with a woman without kissing or and regardless of how well she kisses. On the other hand most women will not have sex with out kissing first and the quality of kissing is relevant to engaging in sex.
The reason men initiate French kissing according to research because saliva contains testosterone and thereby increases the sex drive of their mate. In addition tongue to tongue kissing allows a man to assess a woman’s estrogen level and predict her fertility.
“There is evidence that saliva has testosterone in it,” said Rutgers University anthropologist Helen Fisher, “and testosterone increases sex drive. And there is evidence that men like sloppier kisses with more open mouth. That suggests they are unconsciously trying to transfer testosterone to stimulate sex drive in women.” 
Hormone levels change after kissing. Specifically cortisol (stress) levels decreased in men and women after kissing, and the longer a couple is together the lower their stress hormones get. Interestingly oxytocin levels increase in men, however women’s levels decreased. One theory is that women need more than a kiss to stimulate attachment and bonding. The act of kissing raises a person’s dopamine which in turn raises the oxytocin level promoting bonding
Finally additional benefits include cardiovascular protection via a rise in blood pressure, prevention of tooth decay via an increase in saliva, in addition men who kiss their wives before heading off to work make more money.
 Philematology: The Science of Kissing. A Message for the Marital Month of June
 http://The original theory was t…
 http://The original theory was t…
 Saliva: Secret Ingredient in the Best Kisses