The exact number of people who have dimples cannot be determined because individuals may acquire or lose dimples, due to weight fluctuations or loss of muscle elasticity. A Nigerian study found that 25 percent of the population had dimples on their cheeks.
Dimples are caused by a shortening of the muscles in the cheeks. They can appear on one or both cheeks. They are a dominant trait, which means that only one parent has to have them in order for them to be present in offspring. However, not all children of parents with dimples have dimples themselves. This makes them what is called an "irregular dominant trait."