[EggsAckley]

Yes.....?

[RightWhale]

Animals, and animal heads come in many sizes. Some even have massive jaw muscles that run up to the cranial crest, but these can also have large heads. We lack the cranial crest since we appear to have physiques that are arrested in development in some respects at the infant stage, but we could have cranial crests and massive mandibular muscles without reducing the internal volume of the brain cavity. Some genetic manipulation ought to do the trick.