Kissing may have moved to the mouth as humans became sensitized to the color red, finding ripe fruits for food. That may have led to a woman's red lips, an indicator of a potentially fertile mate. Modern studies show that the color red makes the heart beat faster and may be the reason why women still use lipstick.
The first mention of a mouth kiss -- "smelling with the mouth" -- was in India's Sanskrit texts in 1500 B.C. Later, in the third century A.D., the Kama Sutra instructed readers to kiss "the forehead, the eyes, the cheeks, the throat, the bosom, the breasts, the lips and the interior of the mouth."
Kissing went on to become an act of greeting or reverence, not only sexuality. Greeks and Romans chronicled kisses between slaves and owners; Christians kissed the hands of priests and popes.
In the Middle Ages among the illiterate, legal documents were marked with an X and sealed with a kiss. But by the time the plague arrived in the 17th century, a kiss became deadly and men were more apt to tip a hat than risk touching lips.
Some of the most memorable kisses have come out of Hollywood.
Burt Lancaster's famous kiss in the surf with Deborah Kerr in the 1953 film "From Here to Eternity," still ranks as the most memorable of all screen kisses, as rated by entertainment writer Erik Lundegaard. Tobey Maguire and Kirsten Dunst ranked second in their upside-down kiss in the 2002 movie "Spider-Man," followed by George Peppard and Audrey Hepburn in the 1961 film "Breakfast at Tiffany's," and Patrick Swayze and Demi Moore in the 1990 move "Ghost."
Kissing can even be good for your health.
According to the American Academy of Cosmetic Dentistry, when people kiss, salivary glands under the tongue and in the cheeks are stimulated to produce more saliva. The water, proteins, electrolytes and mineral salts in saliva keep the mouth healthy.
Some cold medications and painkillers may reduce the flow of saliva and kissing can boost production, they say.
What makes a good kisser?
"I like when he takes charge...but not too aggressive," said Kendra Handy, 21, of Snellville, Ga. "I like to feel engaged -- kissing is about more than just lip."
Ashley Boyce, 21, of Bandera, Texas, said a good kiss has "just the right amount of tongue-to-lips-to-teeth ratio."
And it always has to be an appropriate setting, not a busy street corner or school hallway," she said. "In the 'Wedding Singer' they call it 'church tongue'!"
And women don't have to be gay to appreciate a good kiss with another woman.
Annette Bening told ABC News in a recent interview that her co-star in the film "The Kids Are All Right," Julianne Moore, was "at the top" of her list of great kissers.
"We've actually talked about this," Bening said, referring to Moore. "Because both of us have kissed a lot of guys, OK? That's the bottom line. So, we both agree we'd much rather kiss each other than many of the men we've had to kiss."
What is so breathtaking in private can be repulsive in public.
"The worst public kiss I have ever seen was in Penn Station," said Kelly Freund, a 21-year-old college senior from Massapequa, N.Y. "This woman wearing bright pink lipstick and she was attacking her man. They were in their fifties or sixties, and when she left he turned around and had smeared pink lipstick stains all over and around his mouth."