It’s pretty simple. Skull size and shape is constrained by the birth canal. Once freed from the confines of the womb, the skull can grow and change shape to accommodate brain growth. Brainiacs end up looking like eggheads.
Exactly. Vaginal birth babies are cone heads, then the head rounds and the plates fuse.
C-section babies have round heads.
NOT SCIENCE: “Cradle a newborn and you’ll see that infants start life with elongated skulls, somewhat like Neanderthals”