Don't let this swell your head, but skulls these days are significantly larger than the head bones of centuries past.

UK orthodontists measured 30 skulls from victims of a 14th century Black Death epidemic and 54 skulls of unfortunate sailors who went down with the ship off Portsmouth in 1545 and compared them with x-rays of modern young adults. In particular, scientists found that the size of that part of the skull which houses the frontal lobes--the portion of the brain which sits behind our foreheads and is associated with intelligence--has gained in size while our faces are now less prominent.*

While the researchers acknowledge that humans have increased in overall size in the intervening centuries due in part to better diets, they theorize that our bony brain cases may be swelling disproportionately to changes in the attached body.

*Think Kanamites, the flesh-eating aliens of The Twilight Zone who arrived on earth "To Serve Man."