Dimples are usually considered a dominant trait. In the traditional genetics model, you only need one copy of the gene variant to have dimples, while people without dimples carry two recessive copies. But the real picture is more complicated than your high school biology textbook suggested, and some researchers question whether dimples follow simple inheritance rules at all.
Why Dimples Are Called Dominant
In genetics courses, dimples are a go-to example of autosomal dominant inheritance. The logic is straightforward: if you carry even one copy of the “dimple” gene variant (call it D), you’ll have dimples. You’d need two copies of the recessive version (dd) to have a smooth cheek. This makes dimples behave like a trait where having it is “stronger” than not having it.
That classification comes with a major caveat. Very little formal research has been done on the genetics of dimples, and scientists haven’t identified which specific gene or genes are responsible. MedlinePlus, the genetics resource run by the National Library of Medicine, notes that some researchers say there’s no solid proof dimples are inherited in this neat, predictable way. The dominant label persists mostly because it fits the general pattern observed in families, not because anyone has pinpointed the DNA involved.
What Actually Creates a Dimple
The dimple itself is a structural quirk in a facial muscle called the zygomaticus major, which runs from your cheekbone to the corner of your mouth and pulls your lips upward when you smile. In most people, this muscle is a single band. In people with dimples, the muscle splits into two bundles as it travels across the cheek, a variation anatomists call a “bifid” or double zygomaticus major.
The lower bundle of this split muscle attaches to the skin along its midpoint, creating a tethering effect. When you smile and the muscle contracts, the tethered skin gets pulled inward while the surrounding skin stays put. That small inward tug is the dimple. So what you’re really inheriting isn’t a dimple per se. It’s a variation in how a facial muscle develops, and the dimple is just the visible result.
Predicting Dimples in Children
If dimples do follow the simple dominant model, the math for predicting whether a child will have them works like this:
- Both parents have dimples (both heterozygous, Dd x Dd): about a 75% chance the child will have dimples. Three out of four possible gene combinations include at least one D allele.
- One parent has dimples (Dd), one doesn’t (dd): about a 50% chance. Half of the possible combinations carry the dominant allele.
- Neither parent has dimples (dd x dd): essentially 0% chance under this model, since neither parent has a D allele to pass along.
These numbers assume a single gene controls the trait and that one dominant copy is enough to produce visible dimples. In reality, the probabilities are rougher estimates than they appear. Because the specific genes haven’t been identified, and because factors like facial fat distribution and muscle structure also play a role, real-world inheritance doesn’t always match the textbook predictions cleanly.
Why the Simple Model Falls Short
Several observations suggest dimples aren’t as straightforward as a single dominant gene would predict. For one, some people have a dimple on only one cheek. A simple dominant trait should affect both sides of the face equally, since every cell carries the same DNA. Unilateral dimples hint that something beyond genetics, possibly random variation in how the facial muscles develop in the womb, plays a role.
Dimples can also change over a lifetime. Some children are born with prominent dimples that fade or disappear entirely as they grow, while others develop dimples later. Changes in facial fat, skin elasticity, and muscle tone with age can all alter whether that tethering effect is visible. A purely genetic trait wouldn’t be expected to come and go this way, which suggests that anatomy and environment interact with whatever genetic predisposition exists.
It’s also possible that dimples are influenced by multiple genes rather than just one, a pattern geneticists call polygenic inheritance. Traits controlled by several genes don’t follow clean dominant-recessive ratios, which would explain why dimples sometimes skip generations or appear unexpectedly in families where neither parent seems to have them.
What This Means for You
If you’re trying to figure out whether your future children might have dimples, the dominant model gives you a reasonable starting framework. Two dimpled parents are more likely to have dimpled kids than two parents without dimples. But treat those 75% and 50% figures as ballpark numbers, not guarantees. The genetics of dimples are far less settled than traits like blood type or eye color, where the responsible genes have been mapped in detail.
The honest scientific answer is that dimples are probably influenced by genetics and probably behave in a roughly dominant pattern, but nobody has proven this definitively. They sit in a category of traits that get oversimplified in textbooks because they’re easy to observe and fun to talk about, even though the underlying biology remains surprisingly unstudied.