Dimples are charming indentations that appear on a baby’s cheeks, but their presence in infancy does not guarantee they will remain throughout life. A dimple’s visibility is a complex interplay of facial anatomy, the amount of subcutaneous fat, and genetic inheritance. Understanding the physiological mechanics behind these features helps explain why some baby dimples disappear while others become a permanent part of an adult’s smile.
The Anatomy Behind Facial Dimples
A cheek dimple is an anatomical variation related to the Zygomaticus major muscle, which pulls the corners of the mouth up and back when a person smiles. In individuals with dimples, this muscle is often structurally different, sometimes referred to as a bifid or double muscle.
This variation means the muscle divides into two bundles as it travels to the corner of the mouth. One bundle attaches directly to the overlying skin and connective tissue instead of only to the corner of the mouth. When the muscle contracts during a smile, this dermal attachment pulls the skin inward, creating the characteristic depression known as a dimple. This tethering effect is the underlying structural cause of a genetically inherited dimple.
Why Baby Fat Makes Dimples Prominent
The prominence of dimples in infants is influenced by significant fat deposits in the cheeks. This subcutaneous fat is medically known as the buccal fat pad, which contributes to the characteristic roundness of a baby’s face. The buccal fat pad is a well-developed structure in newborns and infants.
This substantial volume of fat pushes the facial tissues outward, making the cheek fuller. Even a minor muscle-to-skin tether, which might not be visible in an adult face, can become exaggerated by the surrounding fat. When the baby smiles or cries, the muscle contracts, and the large amount of cheek fat makes the resulting indentation appear deep and noticeable.
As a child grows, typically between the toddler years and early childhood (around 18 months to 4 years old), the buccal fat pads naturally begin to shrink. This reduction in volume causes the face to thin and lose its infant plumpness. If the dimple was primarily visible due to the bulk of the baby fat and not a strong, underlying muscle tether, the indentation will fade as the fat recedes. This process explains why many dimples that appear in infancy are only temporary.
When Dimples Become Permanent
For a dimple to persist into adulthood, the underlying cause must be the anatomical variation of the Zygomaticus major muscle, rather than the temporary presence of baby fat. If the inherited muscle structure creates a strong dermal attachment, the dimple will remain visible even after the facial fat has decreased. This structural variation is a genetically inherited trait, frequently passed down through families.
While the exact genes involved are not fully identified, the trait is described as a dominant one, meaning a child has a higher likelihood of inheriting it if a parent has dimples. Therefore, a permanent dimple is structure-dependent, a result of a fixed muscle variation that pulls the skin. The temporary dimples of infancy, in contrast, are fat-dependent, disappearing when the baby fat pads shrink and the face matures.