These 11 Facial Expressions Have Helped Humans Survive Since Cave Times
Those goofy faces you make when you're surprised or in awe? They may have evolved from reactions that helped your ancestors survive.
Recognizing facial expressions is a crucial part of emotional IQ, although there could be such a thing as too much emotional intelligence. The origin of facial expressions can help us understand what they signify, according to researcher Daniel Lee of the University of Colorado Boulder. His theory is that expressions evolved for functional reasons first, to gain information about our surroundings to increase our chances of survival. Wide eyes when we’re afraid, for example, help us take in more visual stimuli, like a camera lens opening. “Fear prioritizes sensitivity—getting more information,” Lee says. “Wide eyes that enhance sensitivity for the expresser transmits information sensitivity to the receiver.” Lee has published evidence that this expression was socially co-opted—it became a signal to others—from its sensory-gathering origins.
An open mouth
When you see jaw-dropping photos of the most beautiful country in the world, your mouth literally sags open. But why does this happen when we’re surprised or in awe? Although we may not associate these emotions with fear, they are also info-gathering expressions and have many of the same functions. “We found that fear expressions, including mouth stretching, are associated with increased air intake, which is related to gathering sensory information,” Lee says. Getting in more oxygen may have helped us prepare for fight or flight when we were surprised. As it became an emotion, vocalizing that air intake may have also communicated this surprise, he says.
People could be judging you based on these subtle traits—including the expression in your eyes. So you might want to avoid squinting at people, which can indicate disgust. In his research, “while fear expressions widened the face, disgust oppositely narrowed it,” Lee says. “Disgust prioritizes discrimination, or reducing information and being concerned about what something is specifically.” Think of squinting to make your vision sharper, like when looking for a predator among the trees. Socially, this “discriminating” expression came to signify discriminating against others as well. Think about that the next time you give someone the stink eye!
Smiling really is contagious—when we see someone showing their pearly whites, we are socially cued to reciprocate. But why did people start smiling in the first place? Although Lee says we still don’t know the answer, some scientists have theories. In primates, research has shown that open-mouthed expression that shows teeth can be considered a “play face” indicating submission. It’s even possible that a display of fangs, which would have indicated fear, could have evolved into a submissive expression, as if to say, “Hey, I’m no threat!” “The expression seems to deflect the dominant’s aggression, so it’s a sign of submission, non-hostility, or appeasement, resulting in the dominant leaving them alone,” Janice Porteous, a researcher at Vancouver Island University in Canada who studies the evolution of laughter, told Live Science.
Nose wrinkles and lip curls
Your husband’s most disgusting habit—yes, we’re talking flatulence—may have you wrinkling your nose or curling your lip, and here’s why: Nose wrinkles and lip curls are more signs of disgust, and they help lessen our sense of smell by narrowing our nasal passages. “Disgust seems to be associated with reduction and discrimination of sensory information,” Lee says about his research. “These [expressions] were associated with reduced sensory information.” The evolutionary function could have been to protect us from harmful odors, or to help us decide whether a piece of meat was okay to eat.
You want the secret to a picture-perfect smile, but it may not just be in the mouth, according to science. Lee’s work has also shown that temporal wrinkles (a.k.a. crow’s feet) are associated with joy. Research has proven a smile with laugh lines to be considered more authentic by observers, and it even has a name to honor the scientist who discovered it: the Duchenne smile. But the evolutionary significance of these joy-displaying eye wrinkles isn’t yet clear-cut, especially since eye narrowing is generally connected to disgust and anger. “Alongside the evidence that the Duchenne smile is genuine or more intense, there’s also evidence that the same crow’s feet indicated stronger negative emotions,” Lee says.
According to new theories, there are 27 different emotions you can feel—a big leap from the traditional six of joy, fear, disgust, anger, sadness, and surprise. Anger is pretty tough to mistake: When someone is boiling mad, you can practically see steam coming out of their flared nostrils. “Anger and disgust are similar in structure,” Lee says, with both being expressed by the nose. “There’s other evidence that anger emotions are associated with fighting action, such as increased blood to extremities,” he says. Flared nostrils could also signify preparing for a fight—research suggests this anger signal makes the person appear tough and threatening.
There are nine types of anger—but they all could be displayed by a tense mouth with lips pursed together. Although Lee says we’re not sure of the origins of some anger-specific facial features, primatologists have compared this human look to the “bulging lips face” in chimpanzees. As with flared nostrils, they may signify strength and intimidation to humans as well as chimps. Plus, compressed lips reduce our sensory input, so it could be that we’re protecting our mouths from anything harmful getting in.
Scientists use this movie clip to make people sob their eyes out—and when they do, they are probably showing the classic downturned mouth. “We do have evidence that sad faces are the physical opposites of happy faces, similar to how fear and disgust are physical opposites,” Lee says. Although at least one study shows that the presence of tears has an effect on the perception of sadness from others, the sad frown is also universally recognized (and perhaps one of the most used emojis). The droopiness of the facial muscles could signify defeat or giving up—research has shown toddlers use sad facial expressions most often and intensely to elicit support from their mothers.
Science can tell you what these eyes are saying—and the eyebrows are part of that expression, too. Because humans don’t have much hair on their faces, eyebrows stand out, allowing them to become communication devices. In Lee’s study, the distance of the eyebrow to the eye as well as the shape and curve of the eyebrow revealed emotions when study participants were shown pictures of only eyes. “They seem to be coincident with the eyes, which may enhance their widening and narrowing perception,” Lee says. So for example, raised eyebrows widen the eyes when conveying surprise, but narrow the eyes when signaling disgust. “There’s also some evidence that lower eyebrows, associated with males, convey social dominance,” Lee says. This could be why angry faces often have furrowed brows.
The “not” face
Although it may seem like a modern creation, the “not” face was scientifically shown in a recent study to be a new and universal facial expression to add to the list. (Think of it as the face you’d make when someone says something you totally disagree with.) A composite of anger, disgust, and contempt, it was displayed by English, Spanish, and Mandarin speakers in the study, as well as users of American Sign Language (ASL). “To our knowledge, this is the first evidence that the facial expressions we use to communicate negative moral judgment have been compounded into a unique, universal part of language,” study author Aleix Martinez, a cognitive scientist at Ohio State University, said in a press release. The researchers surmise that this expression of disapproval could have been evolved from a means to convey danger to others.