Ectrodactyly is an inherited dominant genetic mutation. Some have theorized that the mutation may have adaptive benefit if it aids in tree climbing. It’s more likely, however, that the defect remains prevalent in the Vadoma because of a small genetic pool among the Vadoma. It is against tribal law for members to marry outside the group.
Ectrodactyly occurs at lower rates throughout the world and can be caused by a number of human gene defects, a common one being a mutation of the 7th chromosome. It is also associated with hearing loss. Though ectrodactyly itself is fairly rare, occurring in 1 in 90:000 births, limb defects occur in roughly 1 in 1000 births, only slightly less then the rate of identical twins.