Why would people lock lips and swap spit?

The kiss’ allure is a matter of ongoing psychological and physiological research. Some suggest kissing helps humans size up potential mates. When going in for a smooch, one might encounter bad breath, for example, which would typically be a turnoff. That breath might also warn some part of your brain of decay, diseases or other indicators of unfitness. 

And that saliva passed mouth to mouth contains hormones and other compounds that may give the brain clues to determine a kissing partner really is suitable as a match.

Clear evidence exists that humans had sexual relations with Neanderthals—the proof can be seen in our DNA. But did they kiss? 

Scientists studying Neanderthal tooth plaque uncovered the genetic signature of a 48,000-year-old microorganism still found in human mouths today, and different from those of the era’s Neanderthals. How did it get there? 

Read more