40,000 years ago, our closest ancient human relatives did something that changed the manifestation of relationship, bonding forever

Kiss is often seen as one of humanity's most personal expressions of affection. It symbolizes love, trust, friendship, and emotional connection across cultures. But what if this familiar gesture is far older than human civilization itself? New evolutionary research suggests that kissing may have deep biological roots, stretching back millions of years—and that Neanderthals, our closest ancient human relatives who disappeared around 40,000 years ago, likely shared this behavior with modern humans.

The findings offer a fascinating glimpse into the origins of human relationships and suggest that kissing may have played a much larger role in social bonding than previously believed, as per BBC News report.

Origin of Kissing


To investigate the origins of kissing, researchers examined the behavior of numerous animal species and compared similarities across evolutionary lineages. Their goal was to determine when this form of social interaction first appeared and whether it predates modern humans. To avoid confusion, the scientists established a precise scientific definition of a kiss. Rather than describing it romantically, they defined kissing as non-aggressive, directed oral-to-oral contact involving movement of the lips or mouthparts without any transfer of food.

Using this consistent definition allowed researchers to compare behavior across a wide range of species and reconstruct an evolutionary family tree of kissing.

Kissing May Be Millions of Years Older Than Humans

The research points to an astonishing conclusion: kissing likely evolved around 21.5 million years ago among the ancestors of today's great apes. Lead researcher Matilda Brindle explained that humans, chimpanzees, and bonobos all engage in behavior that matches the scientific definition of kissing. Since these species inherited many characteristics from a common ancestor, researchers believe that ancestor probably kissed as well.

If this interpretation is correct, kissing is not a uniquely human invention but an ancient social behavior passed down through millions of years of evolution.

Neanderthals Probably Shared the Same Behavior

One of the study's most intriguing conclusions concerns Neanderthals, who lived alongside early modern humans before disappearing roughly 40,000 years ago. Researchers concluded that Neanderthals likely kissed too.

This finding is supported not only by comparisons with living primates but also by earlier genetic research. Scientists studying ancient DNA discovered that modern humans and Neanderthals shared a specific oral microbe—a type of bacteria commonly found in saliva. The simplest explanation is that the two species exchanged saliva repeatedly over many thousands of years.

While saliva can be exchanged in several ways, kissing provides one plausible mechanism. Combined with behavioral evidence from living primates, this strengthens the idea that kissing formed part of Neanderthal social life.

Kissing More Than Romance

Modern culture often associates kissing with romance, but biology tells a broader story. Across many animal species, oral contact serves multiple social purposes. It can reinforce trust, reduce tension, strengthen family relationships, promote cooperation within groups.

The study identified behaviors fitting the scientific definition of kissing not only in primates but also in wolves, prairie dogs, polar bears, and even albatrosses. Polar bears, researchers noted, display particularly enthusiastic versions involving extensive tongue contact. These observations suggest that oral contact evolved independently or was preserved because it strengthened important social relationships.

Evolution of Human Bonding

Relationships have always been central to human survival. Early humans depended on cooperation to hunt, gather food, protect children, and respond to environmental threats. Behaviors that strengthened trust and social cohesion would have offered significant evolutionary advantages.

Simple gestures of affection—including touching, grooming, hugging, and perhaps kissing—may have helped maintain stable family groups and broader communities. Over countless generations, these behaviors became deeply embedded in human social life. Today's emotional significance of a kiss may therefore reflect millions of years of evolutionary history rather than merely cultural tradition.

Every year, advances in genetics, archaeology, and evolutionary biology reveal surprising insights into humanity's past. Not long ago, Neanderthals were commonly portrayed as primitive and lacking sophisticated social behavior. Evidence increasingly indicates that Neanderthals cared for injured companions, created tools, buried their dead, produced symbolic objects, and likely maintained emotionally meaningful relationships.

The possibility that they also kissed further narrows the perceived gap between them and modern humans. Instead of appearing fundamentally different, Neanderthals increasingly resemble close relatives who shared many familiar behaviors.

Although the research focuses on ancient history, it also highlights something timeless about human nature. People often think of affection as uniquely human, yet evolution suggests many forms of emotional bonding have remarkably deep origins. The instinct to comfort loved ones, express trust, and strengthen relationships may be rooted in behaviors that existed millions of years before modern civilization emerged.

Recognizing these ancient connections reminds us that cooperation—not competition alone—has been one of humanity's greatest strengths. Relationships have always helped individuals and communities survive.

Timeless Connection Across Millions of Years

The image of Neanderthals sharing affectionate gestures may seem surprising, but it reinforces an increasingly important scientific message: humanity's story is one of continuity rather than sharp division. From great apes living over 21 million years ago to Neanderthals walking Ice Age landscapes and modern humans building today's interconnected societies, the desire to create meaningful social bonds appears to have remained remarkably consistent.