A recent study indicates that the American skull has grown bigger and taller since the 19th century. The measurements of hundreds of skulls of white Americans born between 1825 and the 1985 suggest that their typical noggin height has grown by about a third of an inch (eight millimeters).
Researchers at the University of Tennessee's Forensic Anthropology Center routinely examine skulls to try to determine sex and race of the craniums so if police officers discover just a skull, there are guidelines for extricating information about it. The database of skulls and bodies has steadily increased to include people who were born and died in the 20th century, whereas prior the skulls were from people born in the 19th century.
The team examined 1,500 skulls from the mid-1800s to the mid-1980s and what they found is that the average height from the base to the top of the skull in men increased by eight millimeters (0.3 inches), while skull size grew by 200 cubic centimeters, a size equal to the cork ball. In women, skull height increased by seven millimeters and skull size increased by 180 cubic centimeters. Overall, skull height has increased 6.8 percent since the late 1800s, compared with a 5.6 increase in body height and a 2 percent increase in femur (thigh bone) length. The researchers also noted that skull height has continually changed while the increase in body height has recently slowed or stopped.
Since the beginning of the first Homo species, human skulls evolved to be increasingly bigger until about 30,000 years ago, when head size plateaued. And about 5,000 or 6,000 years ago, when agriculture took off in earnest, skulls began shrinking. The cause of the shrinkage is a mystery, but scientists have tentatively fingered more efficient brain wiring and easier access to food and safety-the idea being that people no longer had to be especially smart to survive. Before a decade, the team was measuring skeletons and saw signs that the shrinking trend may be reversing. Since then, they've amassed data on 1,500 skulls spanning 160 years.
Over the past 100 years, life in America changed dramatically. People no longer toil in the fields, and they don't struggle to consume enough calories. The problem arises because the Americans have too much food and not enough physical activity. Hence their bodies don't have to divide fewer calories between the body and the brain, so enough energy can go to the brain, allowing it to balloon. Improved medicine also contributes to larger heads-- in the past babies with bulbous heads could not escape the birth canal and many died. With the increase of C-sections, more and more of these big-headed babies make their into the world.
"As we continue to have excess calories then I am guessing that the brain can continue to increase in size. There obviously has to be some upper limit," says Richard Jantz, professor emeritus.
