Clusters of genetic mutations in isolated populations are common. Look at the pygmies of Africa, the Inuits that have a completely different metabolic system and the Asians and American Indians that lack the gene to process alcohol.
All of the skull abnormalities found across the globe are all medically attributable to the binding process and/or the genetic variations of the local population. Altering the brain cavity can also change the pressure on certain regions of the brain causing changes in things like HGH levels that regulate bone growth. This is particularly relevant to the claimed oversized jaws that are common in over production of HGH.
