Experts say kissing evolved from sniffing, which people did centuries ago as a way of learning about each other.
"At some point, they slipped and ended up on the lips, and they thought that was a lot better," said Vaughn Bryant, an anthropologist at Texas A&M University and an authority on the evolution of human kissing. "You got a lot more bang for your buck."
For most of early human history, smell was more important than any other sense for human relationships, said Sheril Kirshenbaum, author of "The Science of Kissing." People would use smell to determine a person's mood, their health and their social status, she said.
"There were a lot of sniff greetings," said Kirshenbaum, director of the Project on Energy Communication at the University of Texas. "They would brush the nose across the face, because there are scent glands on our faces, and over time the brush of the face became a brush of the lips, and the social greeting was born that way."
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