Having an extra finger or toe or polydactyl is more common in some ethnic groups. It is caused by genetic factors. It is often inherited as autosomal dominant characteristic.

It can be also caused by a genetic disease. The gene responsible for determining polydactyl is located in chromosome seven and it is equally probable to occur in males and females.Stats show that 1 in 500 children, has the condition. More than a hundred diseases has polydactyl as their symptom.