it could be a genetic mutation, but those are really rare, i dont think in the medical field in my knowledge has ever came across such a weird shape skull. Even babies with defects, brain dmg, brain problem or babies who are stuck together at birth, or babies with 6-figners/toes, their skull are all the same, their body structure if not 100%, is at least 85% the same. Maybe if a bone is shorter than a certain bone, arguable yes, but now we're talking about the skull. I dont think a genetic mutation can affect the shape of the skull that much. Not to mention the skull of the starchild belonged to a "boy". I dont think normal/abnormal boys skull would be that small size.