This is a love story: During the spring of 2008, long before they produced evidence of humanity’s first recorded kiss, Sophie Lund Rasmussen and Troels Pank Arboll clasped lips in their first good-night snog. They met a week earlier at a pub near the University of Copenhagen, where both were undergraduates. “I had asked my cousin if he knew any nice single guys with long hair and long beards,” Dr. Rasmussen said. “And he said, ‘Sure, I’ll introduce you to one.’”

Dr. Arboll, in turn, had been looking for a partner that shared his interest in Assyriology, the study of Mesopotamian languages and the sources written in them. “Not many people know what an Assyriologist actually does,” he told her.

“I do,” said Dr. Rasmussen, who had taken some of the same classes.

Dr. Arboll, now a professor of Assyriology at the university, said, “When I heard that, I knew she was a keeper.”

Three years later they wed. Dr. Rasmussen is now an ecologist at the University of Oxford’s Wildlife Conservation Research Unit and Aalborg University in Denmark.

One night over dinner in 2022, the couple discussed — as scientists in love do — a new genetic study that linked modern herpes variants to mouth-to-mouth kissing in the Bronze Age, roughly 3300 B.C. to 1200 B.C. In the paper’s supplementary materials, a brief history of kissing pinpointed South Asia as the place of origin and traced the first literary buss to 1500 B.C., when Vedic Sanskrit manuscripts were being transcribed from oral history.

The researcher, at the University of Cambridge, suggested that the custom — a lip-kissing precursor that involved rubbing and pressing noses together — developed into hardcore smooching. She noted that by 300 B.C. — about when the Indian how-to sex manual, the Kama Sutra, was published — kissing had spread to the Mediterranean with the return of Alexander the Great’s troops from Northern India.