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.
But the couple believed that wasn’t its start. “I told Sophie that I knew of even older accounts written in both the Sumerian and Akkadian languages,” said Dr. Arboll, whose expertise is ancient accounts of medical diagnoses, prescriptions and healing rituals.
“So after dinner, we double-checked,” said Dr. Rasmussen, who specializes in hedgehogs.
They consulted cuneiform texts on clay tablets from Mesopotamia (modern-day Iraq and Syria) and Egypt for clear examples of intimate kissing. Their investigation resulted in a commentary recently published in the journal Science that pushed back the earliest documentation of kissing by 1,000 years and upended the hypothesis that people from a specific region were the first to kiss and tell.
The Danish husband-and-wife team maintain that since at least the late third millennium B.C., kissing was a widespread and well-established part of romance in the Middle East. “Kissing was not a custom that emerged abruptly in a single point of origin,” Dr. Arboll said. “Instead, it seems to have been common across a range of cultures.”
Etched in clay
Dr. Arboll and Dr. Rasmussen proposed that the earliest account of kissing was etched into the Barton Cylinder, a clay tablet that dates to around 2400 B.C. The object was unearthed in the ancient Sumerian city of Nippur in 1899, and named after George Barton, the professor of Semitic languages at Bryn Mawr College, who translated it 19 years later. It is currently housed in the Museum of Archaeology and Anthropology at the University of Pennsylvania, where, from 1922 to 1931, Dr. Barton taught Semitic languages and the history of religion.
The artifact’s narrative involves the Sumerian creation myth and problems with food supplies in Nippur, the original religious capital of Babylonia and the seat of worship for Enlil, ruler of the cosmos. In the second column of text, a male divinity, possibly Enlil, has sex with the mother goddess Ninhursag, the sister of Enlil, and then kisses her. Amid this godly frolicking, the male divinity plants the seed of “seven twins of deities” in her womb.
Gonzalo Rubio, an Assyriologist at Penn State University, said the most compelling part of the story is the sequence of events. “In the portrayals of the act of kissing in Sumerian literature, the subjects have sexual intercourse first and only afterward do they kiss,” he said. “It is afterplay of some sort, rather than foreplay.”
Although the existence of Mesopotamian kissing records may be earthshaking to philematologists, the academics who study the decidedly sober science of the kiss, it is old news to Mesopotamian scholars. “In the small, specialized field of Assyriology, there is a tendency to focus inward and not so much outward,” Dr. Rasmussen said. “As much as Assyriologists like to argue among themselves, they don’t really talk to other people.”
Dr. Rubio, who was not involved in the project, praised Dr. Arboll and Dr. Rasmussen for effectively rewriting the history of kissing. “They aimed to set the record straight and came to correct such a reductionist approach to human behavior,” he said.
Was a Sumerian kiss just a kiss? Dr. Arboll said that in the earliest passages, kissing was described in relation to erotic acts, with the lips as the locus. In Akkadian, a Semitic language related to Hebrew and Arabic of today, he and Dr. Rasmussen found that references to kissing fell into roughly two categories: the “friendly-parental” and the “romantic-sexual.”
The former is a display of familial affection, respect or submission, such as when a royal subject kisses the feet of a ruler. “The sexual-romantic kiss occurs in relation to a sexual act or in relation to love,” Dr. Arboll said. Unlike the friendly-parental variety, it is not culturally universal.
“Lip-kissing has been observed in chimpanzees and bonobos, our closest living relatives,” Dr. Rasmussen added. While the platonic chimp kiss determines compatibility, bonobos canoodle for sexual arousal — their erotic contact ranges from oral sex to intense tongue-twisting. “The kissing practices of these primates hints at something fundamental that goes way back in human history,” Dr. Rasmussen said.
Cue the chemistry
Sumerian written history goes back to the 27th century B.C. and more or less ends a millennium later when the civilization collapsed after an invasion by the Elamites. It was left to the Republicans of ancient Rome, for whom bussing was both a science and a high art, to formulate a hierarchy of kisses and provide each type with an appropriate name. The osculum, a chaste but affectionate peck on the hand or cheek, was used as a greeting; the basium was a closed-mouth, lip-on-lip affair between close friends; the savium was the full works — what we now call a French kiss.
In ancient Mesopotamia, Dr. Rasmussen said, smooching outside of marriage was discouraged. He came across one text, from 1800 B.C., that detailed how a married woman was almost led astray by a soul kiss from a male admirer. Necking with someone who was not supposed to be sexually active was regarded as a crime on par with adultery. “Kissing a priestess was believed to deprive the kisser of the ability to speak,” Dr. Arboll said.
For Romans of the imperial era, kissing a lover in public was also considered indecent. It may also have been considered a health risk. In the first century A.D., the emperor Tiberius tried to outlaw kissing at state functions, likely because of an epidemic of cold sores. Dr. Arboll noted that a substantial corpus of medical writings from Mesopotamia mentioned an ailment called bu’shanu, whose symptoms resembled those of the herpes simplex infections. “The disease appeared mainly in and around the mouth and pharynx,” Dr. Arboll said. “Its name derives from a verb meaning ‘to stink.’”
In “The Science of Kissing: What Our Lips Are Telling Us,” Sheril Kirshenbaum writes about the chemistry of attraction, how a kiss locks two people together in an exchange of colors, tastes and textures. Dr. Rasmussen believes that kissing evolved as a way of sizing up potential partners through their scent.
“With both humans and hedgehogs, it’s all about finding the strongest, healthiest mate to produce the strongest, healthiest offspring,” she said. “So you unconsciously evaluate a person’s suitability through chemical cues like bad breath, which might indicate bad teeth, which might indicate bad genes.”
Dr. Rasmussen still recalls that first tender kiss with Dr. Arboll, which bore the aroma of the hibiscus tea she had just fixed him. What is a kiss? In her memory, it echoed a line from the poet Robert Herrick: “The sure, sweet cement, glue and lime of love.”