The meaning and significance of the smile continues to prove itself as one of the most complex human expressions.

An old adage goes that it takes 22 muscles to smile and 37 to frown, the differential designed to encourage the former. This has long been proven false by scientists (even if the exact number of muscles it does take isn't strictly agreed upon), but the precept says a good deal about the significance of something as simple as upturned mouth corners. The act of smiling has the power to communicate a vast number of emotions—and how those emotions are interpreted has changed and been closely documented by art over time.

Researchers believe that smiling is intimately linked with our evolutionary past, an important tool for conveying information and gauging social situations. But its meaning fluctuates depending on the time and place. Though it can express joy, a smile in the wrong scenario might signal a lack of intelligence—something often used to create racist caricatures—or even a brace against unpleasant news. People only have to look at the increasing iterations the smiling emoji develops with each software update on their phone to get a sense of all the meanings a smile can project.

Jan van Eyck, "Arnolfini Portrait," 1434

For much of art history, smiling was simply impractical as subjects wouldn't be able to hold the expression long enough for artists to capture. Scholars also theorize that a lack of oral hygiene in most societies deterred most artists from documenting smiles as well. But in the present day, as in centuries past, smiles are as much an economic signifier as a display of emotion. Having what is generally accepted to be a great smile is often predicated on having the financial means to care for and correct issues with teeth—which could be why wealthy and upper middle class subjects have historically been shown smiling more than frequently.

But wealth was just one factor. Author Colin Jones traced the development of the smile showing teeth in 18th-century French paintings, demonstrating how they emerged slowly between 1700 and 1780. Jones' research suggests that the gradual appearance corresponded to the fading out of the era's commonly held aristocratic perception that smiling and laughter were signs of bad manners and poor self-control. However, that feeling was by no means universal. The general derision toward smiles in art was primarily a Western one linked to early Christian attitudes. In contrast, many historic Eastern artworks used the smile to signify knowledge and enlightenment.

Statue of a smiling Buddha in Thailand's Wat Mahathat Temple.

Today, smiling in photographs has become the defacto facial expression. Film advertisements of the early- and mid-20th century led the way in solidifying the convention as new technology made the quick capture of a smile possible for the first time. Yet this convention also speaks to the smile's malleability. Though it's considered standard practice to smile in photographs, it does not necessarily signal the occasion is a happy one. It wouldn't be out of the ordinary for a family to smile in a group picture, even if that picture was snapped after a memorial service, as just one example.

The human instinct to smile is so great that not even the ubiquitous masks of the Covid pandemic could stop them. Scientists think the act of smiling can prove critical to our well-being and is still discernible even when our faces are largely obscured. But what do smiles really mean when they're not truly visible? And are they still the potent communicators they normally prove to be? Yes and no. The smile is continually evolving and now, its contemporary incarnation is as complex and multifaceted as the emotions underpinning it.