American head shapes have been changing, but why?

  White Americans are the head and face were the changes in the shape of the average, and no one knows quite why, according to new research.
 In the trend may be determined by going back to the mid-1800s, the U.S. got more skulls, higher and narrower, as seen from the front, said Richard Lee Jantz, a husband and wife team of forensic anthropology at the University of Tennessee, Knoxville.