The Huffington Post | By Jacqueline Howard Posted: 05/31/2012 12:58 pm Updated: 05/31/2012 1:48 pm Skull sizes among white Americans are swelling, researchers say. Did the 20th century make us big-headed? Maybe so, since forensic anthropologists at the University of Tennessee in Knoxville found that white Americans' heads are getting bigger and bigger...in size, that is. The researchers studied a…