Why do some people have dimples?

The most common explanation is a variation in the zygomaticus major muscle: in some people it is split into two bundles, and the skin between them dimples when the muscle contracts. Dimples are often said to be a dominant genetic trait, but researchers now consider the inheritance irregular and not fully understood. Some babies have dimples caused by baby fat that disappear as they grow, while others develop them later. Chin dimples, or cleft chins, arise differently, from incomplete fusion of the jawbone or muscle. Many cultures consider dimples attractive or lucky.