If someone complains that a person has a big head, it’s normally considered a dig at the enormity of that person's ego. But when it comes to white Americans, being labeled as big-headed shouldn’t be considered a criticism as much as an apt description: Over the past 150 years, the size of white Americans’ craniums have actually increased in size.

Researchers at the University of Tennessee’s Forensic Anthropology Center (what Mary Roach calls "the body farm" in her book “Stiff”) 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 gleaning info 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.

As researchers Lee Jantz, coordinator of Forensic Anthropology Center, Richard Jantz, professor emeritus, and Joanne Devlin, adjunct assistant professor, catalogued 1,500 noggins they observed that white people who were born in the 20th century had bigger heads.

They looked at white skulls because they wanted to have a large sample and they don’t have as many black and Hispanic skulls. When people decide to donate their bodies to science, some of those bodies end up at the Forensic Anthropology Center. Historically, more white people have donated their bodies to science than black or Hispanic people, but Jantz suspects that as the makeup of America changes, the center will receive more donations from black and Hispanic people.

The height of white male skulls has increased by eight millimeters and the overall skull has grown by 200 cubic centimeters. For women, cranium height increased by seven millimeters and overall by 180 cubic centimeters.

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“The basic thing that we observed over the course of looking at crania that belong to people born from 1820s to 1980s, is that the cranium has gotten higher and narrower,” says Richard Jantz, who is married to Lee.

“If you just look at a side view of the skull, what you would see is the distance from top to bottom increased, and if you look at a front view of the skull, you would see the distance from side to side decreased.”

Bigger heads typically mean bigger brains, and while Richard Jantz and his colleagues did not look at brain size, he suspects brain size also increased. There are several theories why brains might be brawnier.

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. We have too much food and not enough physical activity. This means our 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 babes make it 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.

He suspects that most black Americans would have larger craniums as well, but believes that Hispanic skulls might be smaller. A greater number of the country's Hispanic people are not born in the United States, potentially limiting their access to excess calories and the additional energy needed to grower larger skulls (and bodies). As the generations pass, Hispanic people will probably grow larger as well.

Jantz also notes that Americans mature faster now than they did in earlier centuries. In the 19th century, on average, girls reached menarche at 16 or 17, whereas modern girls reach it by 12 or 13, indicating that humans are growing more rapidly.

To a certain extent, the researchers weren't surprised to learn that noggins increased in size. Jantz says it is obvious that modern Americans look different than their ancestors. He notes there aren't a lot of pictures of obese people from the 19th century. Having access to excess calories leads to taller, fatter, bigger Americans. And while Jantz notes that bigger heads means bigger brains, he hesitates to speculate that bigger brains equal smarter people.

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