India, Sept. 19 -- The oldest known reference to a kiss comes via a clay model from Mesopotamia, dated to 1800 BCE. It takes the form of an image of a couple, on a cuneiform clay tablet, in a story about two Mesopotamian deities. The Rig Veda, dated to at least 1500 BCE, describes the meeting of the lips too. By the 1st century CE, it had become a rampant act that the Roman Emperor Tiberius (14-37 CE) tried to ban at public functions, to control the spread of infections such as herpes. By the 3rd century CE, the Kama Sutra was dedicating entire chapters to the art of kissing.

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The concept of fraternity,one of the three core values of the French Revolution, was often represented by this gesture. In the painting above by Rene Duchemin, t...