US Heads Getting Taller, Leaner Skulls grew faster than bodies during 20th century By Neal Colgrass, Newser Staff Posted Jun 2, 2012 3:30 PM CDT 28 comments Comments A skull worth measuring. (Shutterstock) (Newser) – Americans got pretty big heads in the 20th century, and we're not talking egos here. Forensic anthropologists in Knoxville have analyzed skulls from the mid-1800s to the mid-1980s and found that our heads have become taller, larger, and narrower, reports US News & World Report. The difference is particularly striking from the late 1800s on, when skull height surged by 6.8% compared to only 5.6% in body height. Why the big heads? "The varieties of changes that have swept American life make determining an exact cause an endlessly complicated proposition," says one researcher, but he says better nutrition, lower maternal and infant mortality, and less physical labor are likely suspects. One interesting tidbit: American skulls are also maturing faster, closing a certain bone structure at age 16 in boys and 14 in girls that once closed at around age 20.