Dimples are sometimes caused by a change in a facial muscle called the zygomaticus major

. This muscle is involved in facial expression. ... Because cheek dimples can result from a muscular variation that occurs during fetal development, they're sometimes mistakenly referred to as a birth defect.

Are dimples a birth defect?

A birth defect that is otherwise known as the dimple. For eons, mankind has associated dimples with attractiveness. And yet, those facial depressions are essentially an accident of birth, conferred through genetics.

Why are dimples a genetic defect?

Dimples—indentations on the cheeks—tend to occur in families, and this trait is assumed to be inherited. Dimples are usually considered a dominant genetic trait, which means that one copy of the altered gene in each cell is sufficient to cause dimples.