Dimples: Genetics, Rarity, and Why They Charm
Cheek dimples are often called a dominant trait, but the science is shakier than the textbooks say. What causes them, how common they are, why some kids lose them, and why people find them so appealing.
A smile with dimples gets noticed. Those little dents in the cheeks have a reputation for being charming, and also for being a simple genetic trait you either inherit or don't. The first part is true. The second part is more complicated.
What a dimple actually is
Most cheek dimples are tied to a muscle called the zygomaticus major, one of the main muscles you smile with. It runs from the cheekbone to the corner of the mouth. In some people the muscle is split into two bundles (doctors call it "bifid"). When they smile, the skin over the gap between the bundles gets pulled in, and a dimple appears.
That's why dimples usually show only when someone smiles.
Is it a dominant trait?
You'll often read that dimples are a simple dominant trait: one parent with dimples, good odds the child has them. That's how it was taught for years. But researchers who have looked closely say the evidence for a single "dimple gene" is weak. Some call dimples an "irregular dominant" trait, meaning they run in families but don't follow simple rules.
What we can say:
- Dimples do tend to run in families.
- Two parents with dimples can have a child without them, and the other way around.
- More than one gene and plain chance during development probably play a part.
How common are they?
Studies in different countries have found very different rates, so it depends a lot on the group. In most of them, dimples are common enough that you know several people who have them, but they're not the norm.
Why some kids lose them
Many babies and toddlers have dimples that fade as they grow. Baby cheeks are full of fat, which can create dimples that disappear as the face slims out. Others keep theirs for life. A few people notice dimples appearing later on.
Other kinds of dimples
- Chin dimple (cleft chin): a groove where the two halves of the jawbone or chin muscle didn't fully fuse.
- Back dimples (dimples of Venus): two dents in the lower back, over the joints where the spine meets the pelvis.
- Single dimple: some people have a dimple in only one cheek.
Why they charm
Nobody has a perfect answer, but a few ideas come up:
- Dimples make a smile easier to see, which makes a face look friendlier.
- They often look youthful, since many kids have them.
- They're a little uncommon, and uncommon features get noticed.
Some people even get cosmetic dimple surgery. It's a short procedure, but like any surgery it has risks, and the results don't always look natural.
Related
- Freckles: what they are and who gets them
- Heterochromia: two different colored eyes
- How rare is left-handedness?
Photo: BoyWithDimples Nagarjun by Nagarjun, CC BY 2.0.