“My upper lip becomes moist, while my lower lip trembles! I shall embrace him, I shall kiss him.” —1900-1595 B.C.E. tablet from Sippar, Mesopotamia; translation by Nathan Wasserman, Akkadian Love Literature of the Third and Second Millennium B.C.E.
These breathless lines of cuneiform script, etched into a clay tablet some 4,000 years ago, are among the very first depictions of romantic kissing. But hints from archaeology and DNA suggest that humans were kissing long before they had the ability to tell about it in writing; the amorous act might even be as old as our species. Unfortunately, as kissing caught on so did a side effect—the spread of disease. Now, scientists studying the evolution of persistent pathogens are delving into the history of the kiss and trying to uncover smooching’s longtime role in their transmission.
Troels Pank Arbøll, a cuneiform expert at the University of Copenhagen who specializes in the history of medicine, co-wrote a perspective in Science this Thursday that explores the ancient history of kissing and its role in disease transmission. Arbøll and Sophie Lund Rasmussen pored over cuneiform writings from Mesopotamia, keying in on overlooked references to kissing and medical records describing disease. The study pushes back the often cited date for the oldest written evidence of the kiss, a 3,500-year-old Bronze Age manuscript from India. The authors describe Mesopotamian tablets 1,000 years older but, citing evidence from ancient art and DNA, Arbøll stresses the 4,500-year-old writings shouldn’t be thought of as the original cradle of kissing.
That’s because a kiss is fleeting and doesn’t leave much behind for scientists to uncover. “The origin of sexual romantic kissing must have been way further back into prehistory than we are able to detect with present methods,” Arbøll says.
Kissers may exhibit individual style, but researchers differentiate between two main types of kissing. The first is the type of peck one might expect from family or friends, which appears to be fairly ubiquitous among societies the world over. But the second type, the long, open-mouthed kiss favored by lovers, is the focus of this research.
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.
Kissing also builds pair bonding, and happier couples kiss more, some research shows, though experts can’t say exactly how it works. One reason may be that it simply feels good; while kissing, our sensitive lips and tongues trigger areas of the brain involved in increasing pleasure and decreasing stress.
Nonhuman primates have also been spotted smooching. Bonobos engage in mouth-to-mouth kissing as part of their sexual behavior. Chimps employ platonic kisses, which are part of their social interactions in the group. Might kisses have played the same kinds of roles in early Homo sapiens, meaning our proclivity to kiss could be as old as our species itself? Scientists don’t know.
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? Kissing is a definite possibility, though not the only one, as the two species might have also shared a meal.
Hints exist from art and archaeology as well. The embracing figures in the 11,000-year-old Ain Sakhri sculpture, the oldest to depict people making love, may well be locked in a passionate kiss as well. A lack of facial features makes this open to interpretation.
Cuneiform writing appeared around 3200 B.C.E. and for several hundred years seems limited to humdrum administrative texts. After a while, perhaps inevitably, the subject of amorous relations found its way into the Mesopotamian record—and with them the first references to kissing some 4,500 years ago.
“The first real instances seem to be mythological texts,” Arbøll says. “Obviously the divine world is also a sort of reflection of what goes on among people, but there it seems to have played a role in relation to sexual encounters. So it’s interesting that they envisioned their gods in that way.”
In other Mesopotamian texts, examples of kissing suggest it was a common part of romantic relations between married couples—and a dangerous aspect of desire among some of the unmarried.
In one circa 1900-1595 B.C.E. legal document from the Mesopotamian city of Larsa, as translated by Marten Stol in Women in the Ancient Near East, a woman named Shat-Marduk vows to cut off contact with her apparently illicit lover: “He shall not return [to me], and he shall not suggest to me ‘the man and woman’s thing,’ and he shall not kiss my lips, and I shall not allow him ‘the man and woman’s thing.’ If he invites me to lie in his bosom, then I shall surely report it to the elders and the mayor.”
And Mesopotamia wasn’t the only lip-locking hot spot in ancient times. Arbøll notes that examples from India and Egypt show a wide geographic area in which the sexual kiss was practiced in antiquity.
“This article adds to our historical understanding of intimate human behaviors such as kissing and gives a fascinating insight into the personal lives of ancient Mesopotamians from very early written records,” says Charlotte Houldcroft, a molecular biologist at the University of Cambridge who studies the evolution of disease and wasn’t involved in the new research.
Despite kissing’s long history, it is far from ubiquitous today. A 2015 study of 168 cultures around the globe found that romantic kissing was popular in only about half those groups. And where kissing is common, some people pay a price for the experience.
Diseases including herpes simplex virus 1 (HSV-1), Epstein-Barr virus, human parvovirus and the common cold can be spread by saliva, so kissing can propagate them throughout a population. One study suggests that tens of millions or even 1 billion bacteria can be exchanged during deep kissing.
Medical records show that Mesopotamians didn’t believe that kissing played a role in spreading infectious disease, Arbøll reports in the paper. But it may well have been happening. It’s hard to diagnose disease by translating ancient descriptions in cuneiform text. Still, the Mesopotamian mouth disease known as bu’sanu may have been herpes, the authors note. At least some figures in the ancient world did seem to suspect that the practice had health impacts. In Rome, Emperor Tiberius tried to ban kissing at state functions, likely because it was thought to be spreading herpes. (His efforts were unsuccessful.)
Last year, Houldcroft and colleagues used ancient DNA to sequence genomes of the herpes virus and chart its evolution. They suggested that what’s now the dominant strain, HSV-1, was born 5,000 years ago, during Bronze Age migrations from Eurasia to Europe, and boosted by the rapid rise of a new cultural practice spread among those mixing populations—deep kissing.
The World Health organization estimates that two-thirds of the world’s population under age 50, some 3.7 billion people, are infected with HSV-1.
Arbøll and Rasmussen write that since ancient human remains have also yielded the genomes of numerous pathogens transmitted by saliva, diseases transmissible by kissing have been present even from prehistoric times. But the evidence of kissing’s longstanding popularity makes the theory that the HSV-1 strain arose from a sudden epidemic of kissing, passing from culture to culture, less likely.
“I think that kissing has played a role in disease transmission, but it seems to have been more of a constant way of transmission,” he further explains. “Our suggestion is that because it seems to have this wide distribution in the ancient world, it didn’t rapidly accelerate a disease in any given population.” Given the known cultural mixing between areas of the ancient world, evidenced by the interchange of objects, tools and genes, he feels that kissing would have been well known, if not universally embraced.
“Those that didn’t adopt kissing likely found it disgusting in some way,” Arbøll says, “and they wouldn’t have then just embraced it just because some migrants came and said, ‘Hey, this kissing is a great idea.’”