What are dimples, and why do only some people have them?

looney_tunes

Dimples are visible indentations of the skin, caused by underlying flesh, which form on some people's cheeks, especially when they smile (may be obscured by male facial hair). Dimples are genetically inherited and are a dominant trait. Dimples are usually found on both cheeks. A rarer form is the single dimple, which occurs on one side of the face only. Anatomically, dimples may be caused by variations in the structure of the facial muscle known as zygomaticus major. Specifically, the presence of a double or bifid zygomaticus major muscle may explain the formation of cheek dimples. http://en.wikipedia.org/wiki/Dimple Aug 16 10, 6:09 AM