In 1923, Evangeline I. Gilbert filed a patent for an “appliance for producing dimples,” which was essentially a metal face strap with two knobs that left depressions in the wearer’s cheeks. While it’s unlikely the invention had any lasting effects, its mere existence is evidence that many people consider dimples an attractive, coveted feature.

According to Bustle, the leading theory for the cause of this charming anomaly involves the zygomaticus major, the muscle that runs from your cheekbone to the corner of your mouth, and lifts that corner when you smile. In dimple-less humans, the zygomaticus major is one continuous band; in some of our dimpled counterparts, however, researchers have found that the muscle actually forks near the mouth. When they smile, a dimple appears where this “double or bifid zygomaticus major” splits. That said, scientists haven’t exactly proven that the zygomaticus major is responsible for all dimples—it’s also possible that variations in other facial muscles can affect dimple formation.

How some of us end up with those atypical, dimple-causing facial muscles is still an unanswered question, too. Because it’s common for dimple-cheeked parents to have dimple-cheeked children, many researchers agree that genetics is the key to the mystery. Though it used to be widely believed that dimples were a dominant trait (i.e. if both parents have dimples, their children will always have dimples), it has since been found that this isn’t always the case. Now, as Healthline explains, dimples are more often considered an “irregular dominant trait,” which basically means that there are some exceptions to the rule. Much like multiple facial muscles—rather than just the zygomaticus major—could cause dimples in some people, dimple inheritance could be impacted by a combination of genes, instead of just one.

In short, we definitely don’t know everything there is to know about dimples. What we can be reasonably sure of is this: As adorable as dimples are, they’re probably not worth clamping a metal contraption to your face.

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