Why We've Been Kissing for Millions of Years

The date was perfect. He was witty, remembered your favourite wine, and held your coat as if he’d rehearsed it. At your door, he leaned in. A second or two later, and it was clear: there would be no second date. Why? It’s hard to articulate. It’s as if your body ran a quick check, assessed the situation, and made a decision before you even had a say.

As it turns out, our bodies have been doing this for millions of years.

Millions of Years Ago: The First Kiss

Long before humans, our common ancestor with the great apes lived some 17 to 21 million years ago. Scientists studying primates suggest that this ancestor and its kin were likely the first to kiss. Chimpanzees, bonobos, and orangutans kiss openly, though gibbons and eastern gorillas generally do not.

Scientists define a kiss as lip-to-lip contact without food transfer. When a primate passes food mouth-to-mouth, it is considered nourishment, not affection.

Hundreds of Thousands of Years Ago: Neanderthals and Campfires

When we arrive on the scene alongside Neanderthals, evidence from ancient dental plaque shows we shared oral bacteria. While not definitive proof of kissing, it implies that intimate social gatherings likely involved more than just conversation.

It is curious when you think about it. Kissing is not strictly necessary for survival and easily transmits illness, yet the habit survived the Ice Ages. Nature rarely preserves such habits without a biological purpose.

4,500 Years Ago: Cuneiform Tablets

The first written records of kissing appear in Mesopotamia. Cuneiform clay tablets mention kisses in romantic, friendly, and familial contexts. For the people who invented writing, kissing was as mundane a part of life as beer or taxes.

Not Everywhere and Not Always

We should dispel the myth that everyone kisses. While Hollywood suggests it is a universal human trait, researchers who analyzed 168 cultures found that the romantic lip-to-lip kiss existed in less than half of them. Ethnographers observed no such kissing among tribes in the Amazon or New Guinea. Kissing appears more common in complex, stratified societies; it is less a law of nature and more a cultural trend that waxes and wanes.

1896: The First Kiss on Film

Edison Studios released a short clip of a couple kissing. Though it lasted only seconds, the public was enthralled, and moralists immediately decried it as a sign of societal decay. If you think modern debates about youth culture are new, remember that a two-second clip sparked a century of scandal.

2013: The Marathon

A Thai couple, Ekkachai and Laksana Tiranarat, set a record by kissing for 58 hours and 35 minutes over Valentine’s Day. Guinness World Records eventually retired this category due to the health risks of sleep deprivation and psychological strain. Newer records now incorporate mandatory rest breaks.

Today: What Science Knows About Your Date

Kissing has been studied extensively in recent years. Here is what we know:

Kissing involves the exchange of oral bacteria. Couples who kiss frequently share a similar oral microbiome.

Research suggests a poor first kiss can influence a partner's interest in continuing the relationship. For many women, kissing increases in importance as a relationship develops, whereas many men view it as an additional benefit.

Kissing reduces stress, especially in long-term relationships. Some research suggests couples often tilt their heads to the right when kissing. There is also a hypothesis that we unconsciously assess a partner’s scent and taste during a kiss to determine compatibility. While difficult to prove, the theory remains compelling.

A kiss is a personal and complex part of human connection. While a date involves many elements, the physical interaction during a kiss is a significant moment in determining chemistry.